[lldb] Make that we can call HostInfo::Initialize and HostInfo::Terminate multiple times

[teemperor]

Summary

HostInfo's state isn't actually fully rested after calling ::Terminate. Currently we only reset the
values of all the HostInfoBaseFields but not all the variables with static storage that
keep track of whether the fields need to be initialised. This breaks random unit tests as running
them twice (or running multiple test instances in one run) will cause that the second time
we ask HostInfo for any information we get the default value back for any field.

This patch moves all the once_flag's into the HostInfoBaseFields so that they also get reseted
by ::Terminate and removes all the success bools. We should also rewrite half this code but
I would prefer if my tests aren't broken over the holidays so let's just put some duct tape on it
for now.

[labath]

Yeah, this code could use a rewrite, but this is definitely better...

lldb/source/Host/common/HostInfoBase.cpp

~HostInfoBaseFields() {
     if (FileSystem::Instance().Exists(m_lldb_process_tmp_dir)) {
       // Remove the LLDB temporary directory if we have one. Set "recurse" to
       // true to all files that were created for the LLDB process can be
       // cleaned up.
       llvm::sys::fs::remove_directories(m_lldb_process_tmp_dir.GetPath());
     }
   }
 
+  llvm::once_flag m_host_triple_once;
   std::string m_host_triple;
 
+  llvm::once_flag m_host_arch_once;
   ArchSpec m_host_arch_32;
   ArchSpec m_host_arch_64;
 
+  llvm::once_flag m_lldb_so_dir_once;
   FileSpec m_lldb_so_dir;
+  llvm::once_flag m_lldb_support_exe_dir_once;
   FileSpec m_lldb_support_exe_dir;
+  llvm::once_flag m_lldb_headers_dir_once;
   FileSpec m_lldb_headers_dir;
+  llvm::once_flag m_lldb_clang_resource_dir_once;
   FileSpec m_lldb_clang_resource_dir;
+  llvm::once_flag m_lldb_system_plugin_dir_once;
   FileSpec m_lldb_system_plugin_dir;
+  llvm::once_flag m_lldb_user_plugin_dir_once;
   FileSpec m_lldb_user_plugin_dir;
+  llvm::once_flag m_lldb_process_tmp_dir_once;
   FileSpec m_lldb_process_tmp_dir;
+  llvm::once_flag m_lldb_global_tmp_dir_once;
   FileSpec m_lldb_global_tmp_dir;
 };
 
 HostInfoBaseFields *g_fields = nullptr;
 }
 
 void HostInfoBase::Initialize() { g_fields = new HostInfoBaseFields(); }
 
 void HostInfoBase::Terminate() {
   delete g_fields;
   g_fields = nullptr;
 }
 
 llvm::StringRef HostInfoBase::GetTargetTriple() {
-  static llvm::once_flag g_once_flag;
-  llvm::call_once(g_once_flag, []() {
+  llvm::call_once(g_fields->m_host_triple_once, []() {
     g_fields->m_host_triple =
         HostInfo::GetArchitecture().GetTriple().getTriple();
   });
   return g_fields->m_host_triple;
 }
 
 const ArchSpec &HostInfoBase::GetArchitecture(ArchitectureKind arch_kind) {
-  static llvm::once_flag g_once_flag;
-  llvm::call_once(g_once_flag, []() {
+  llvm::call_once(g_fields->m_host_arch_once, []() {
     HostInfo::ComputeHostArchitectureSupport(g_fields->m_host_arch_32,
                                              g_fields->m_host_arch_64);
   });
 
   // If an explicit 32 or 64-bit architecture was requested, return that.
   if (arch_kind == eArchKind32)
     return g_fields->m_host_arch_32;
   if (arch_kind == eArchKind64)
     return g_fields->m_host_arch_64;
 
   // Otherwise prefer the 64-bit architecture if it is valid.
   return (g_fields->m_host_arch_64.IsValid()) ? g_fields->m_host_arch_64
                                               : g_fields->m_host_arch_32;
 }
 
 llvm::Optional<HostInfoBase::ArchitectureKind> HostInfoBase::ParseArchitectureKind(llvm::StringRef kind) {
   return llvm::StringSwitch<llvm::Optional<ArchitectureKind>>(kind)
       .Case(LLDB_ARCH_DEFAULT, eArchKindDefault)
       .Case(LLDB_ARCH_DEFAULT_32BIT, eArchKind32)
       .Case(LLDB_ARCH_DEFAULT_64BIT, eArchKind64)
       .Default(llvm::None);
 }
 
 FileSpec HostInfoBase::GetShlibDir() {
-  static llvm::once_flag g_once_flag;
-  static bool success = false;
-  llvm::call_once(g_once_flag, []() {
-    success = HostInfo::ComputeSharedLibraryDirectory(g_fields->m_lldb_so_dir);
+  llvm::call_once(g_fields->m_lldb_so_dir_once, []() {
+    if (!HostInfo::ComputeSharedLibraryDirectory(g_fields->m_lldb_so_dir))
+      g_fields->m_lldb_so_dir = FileSpec();
     Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST);
     LLDB_LOG(log, "shlib dir -> `{0}`", g_fields->m_lldb_so_dir);
   });
-  return success ? g_fields->m_lldb_so_dir : FileSpec();
+  return g_fields->m_lldb_so_dir;
 }
 
 FileSpec HostInfoBase::GetSupportExeDir() {
-  static llvm::once_flag g_once_flag;
-  static bool success = false;
-  llvm::call_once(g_once_flag, []() {
-    success =
-        HostInfo::ComputeSupportExeDirectory(g_fields->m_lldb_support_exe_dir);
+  llvm::call_once(g_fields->m_lldb_support_exe_dir_once, []() {
+    if (!HostInfo::ComputeSupportExeDirectory(g_fields->m_lldb_support_exe_dir))
+      g_fields->m_lldb_support_exe_dir = FileSpec();
     Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST);
     LLDB_LOG(log, "support exe dir -> `{0}`", g_fields->m_lldb_support_exe_dir);
   });
-  return success ? g_fields->m_lldb_support_exe_dir : FileSpec();
+  return g_fields->m_lldb_support_exe_dir;
 }
 
 FileSpec HostInfoBase::GetHeaderDir() {
-  static llvm::once_flag g_once_flag;
-  static bool success = false;
-  llvm::call_once(g_once_flag, []() {
-    success = HostInfo::ComputeHeaderDirectory(g_fields->m_lldb_headers_dir);
+  llvm::call_once(g_fields->m_lldb_headers_dir_once, []() {
+    if (!HostInfo::ComputeHeaderDirectory(g_fields->m_lldb_headers_dir))
+      g_fields->m_lldb_headers_dir = FileSpec();
     Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST);
     LLDB_LOG(log, "header dir -> `{0}`", g_fields->m_lldb_headers_dir);
   });
-  return success ? g_fields->m_lldb_headers_dir : FileSpec();
+  return g_fields->m_lldb_headers_dir;
 }
 
 FileSpec HostInfoBase::GetSystemPluginDir() {
-  static llvm::once_flag g_once_flag;
-  static bool success = false;
-  llvm::call_once(g_once_flag, []() {
-    success = HostInfo::ComputeSystemPluginsDirectory(
-        g_fields->m_lldb_system_plugin_dir);
+  llvm::call_once(g_fields->m_lldb_system_plugin_dir_once, []() {
+    if (!HostInfo::ComputeSystemPluginsDirectory(g_fields->m_lldb_system_plugin_dir))
+      g_fields->m_lldb_system_plugin_dir = FileSpec();
     Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST);
     LLDB_LOG(log, "system plugin dir -> `{0}`",
              g_fields->m_lldb_system_plugin_dir);
   });
-  return success ? g_fields->m_lldb_system_plugin_dir : FileSpec();
+  return g_fields->m_lldb_system_plugin_dir;
 }
 
 FileSpec HostInfoBase::GetUserPluginDir() {
-  static llvm::once_flag g_once_flag;
-  static bool success = false;
-  llvm::call_once(g_once_flag, []() {
-    success =
-        HostInfo::ComputeUserPluginsDirectory(g_fields->m_lldb_user_plugin_dir);
+  llvm::call_once(g_fields->m_lldb_user_plugin_dir_once, []() {
+    if (!HostInfo::ComputeUserPluginsDirectory(g_fields->m_lldb_user_plugin_dir))
+      g_fields->m_lldb_user_plugin_dir = FileSpec();
     Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST);
     LLDB_LOG(log, "user plugin dir -> `{0}`", g_fields->m_lldb_user_plugin_dir);
   });
-  return success ? g_fields->m_lldb_user_plugin_dir : FileSpec();
+  return g_fields->m_lldb_user_plugin_dir;
 }
 
 FileSpec HostInfoBase::GetProcessTempDir() {
-  static llvm::once_flag g_once_flag;
-  static bool success = false;
-  llvm::call_once(g_once_flag, []() {
-    success = HostInfo::ComputeProcessTempFileDirectory(
-        g_fields->m_lldb_process_tmp_dir);
+  llvm::call_once(g_fields->m_lldb_process_tmp_dir_once, []() {
+    if (!HostInfo::ComputeProcessTempFileDirectory( g_fields->m_lldb_process_tmp_dir))
+      g_fields->m_lldb_process_tmp_dir = FileSpec();
     Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST);
     LLDB_LOG(log, "process temp dir -> `{0}`",
              g_fields->m_lldb_process_tmp_dir);
   });
-  return success ? g_fields->m_lldb_process_tmp_dir : FileSpec();
+  return g_fields->m_lldb_process_tmp_dir;
 }
 
 FileSpec HostInfoBase::GetGlobalTempDir() {
-  static llvm::once_flag g_once_flag;
-  static bool success = false;
-  llvm::call_once(g_once_flag, []() {
-    success = HostInfo::ComputeGlobalTempFileDirectory(
-        g_fields->m_lldb_global_tmp_dir);
+  llvm::call_once(g_fields->m_lldb_global_tmp_dir_once, []() {
+    if (!HostInfo::ComputeGlobalTempFileDirectory( g_fields->m_lldb_global_tmp_dir))
+      g_fields->m_lldb_global_tmp_dir = FileSpec();
+
     Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST);
     LLDB_LOG(log, "global temp dir -> `{0}`", g_fields->m_lldb_global_tmp_dir);
   });
-  return success ? g_fields->m_lldb_global_tmp_dir : FileSpec();
+  return g_fields->m_lldb_global_tmp_dir;
 }
 
 ArchSpec HostInfoBase::GetAugmentedArchSpec(llvm::StringRef triple) {
   if (triple.empty())
     return ArchSpec();
   llvm::Triple normalized_triple(llvm::Triple::normalize(triple));
   if (!ArchSpec::ContainsOnlyArch(normalized_triple))
     return ArchSpec(triple);