Fix problem where 32-bit statically built lldb-platform cannot find lldb-gdbserver.

[chaoren]

Summary

Adding x86 to supported architectures on x86_64.

Failsafe directory for shared objects and support executables.

[ovyalov]

Please see my comments.

source/Host/linux/HostInfoLinux.cpp

228

Could you check return value of HostInfoPosix::ComputeSharedLibraryDirectory?
You may return true immediately if HostInfoPosix::ComputeSharedLibraryDirectory return true and fall back to GetProgramFileSpec().GetDirectory().

source/Plugins/Platform/gdb-server/PlatformRemoteGDBServer.cpp

222

Do we need this condition only for remote debugging of Linux target? Or is it required for local LLGS debugging as well?
I'm wondering whether an alternative solution is appropriate - override HostInfoLinux::GetArchitecture(..) and put this condition in there. In this case it will be supported either with local or remote debugging, with and without LLGS.

source/Plugins/Process/Utility/RegisterContextLinux_i386.cpp

114

case llvm::Triple::x86:
case llvm::Triple::x86_64:

return g_register_infos_i386;

?

[ovyalov]

lgtm

[chaoren]

source/Plugins/Platform/gdb-server/PlatformRemoteGDBServer.cpp

222

I actually don't need this part for what I'm doing. Just in case I don't break anything without noticing, I'm going to remove this change.

include/lldb/Host/linux/HostInfoLinux.h

public:
 
     static bool GetOSVersion(uint32_t &major, uint32_t &minor, uint32_t &update);
     static bool GetOSBuildString(std::string &s);
     static bool GetOSKernelDescription(std::string &s);
     static llvm::StringRef GetDistributionId();
     static FileSpec GetProgramFileSpec();
 
   protected:
+    static bool ComputeSharedLibraryDirectory(FileSpec &file_spec);
     static bool ComputeSystemPluginsDirectory(FileSpec &file_spec);
     static bool ComputeUserPluginsDirectory(FileSpec &file_spec);
     static void ComputeHostArchitectureSupport(ArchSpec &arch_32, ArchSpec &arch_64);
 };
 }
 
 #endif

source/Host/linux/HostInfoLinux.cpp

if (!g_program_filespec)
             g_program_filespec.SetFile(exe_path, false);
         }
     }
 
     return g_program_filespec;
 }
 
 bool
+HostInfoLinux::ComputeSharedLibraryDirectory(FileSpec &file_spec)
+{
+    HostInfoPosix::ComputeSharedLibraryDirectory(file_spec);
+    if (!file_spec.GetDirectory())
+        file_spec.GetDirectory() = GetProgramFileSpec().GetDirectory();
+    return (bool)file_spec.GetDirectory();
+}
+
+bool
 HostInfoLinux::ComputeSystemPluginsDirectory(FileSpec &file_spec)
 {
     FileSpec temp_file("/usr/lib/lldb", true);
     file_spec.GetDirectory().SetCString(temp_file.GetPath().c_str());
     return true;
 }
 
 bool

source/Plugins/Platform/gdb-server/PlatformRemoteGDBServer.cpp

 {
 }
 
 bool
 PlatformRemoteGDBServer::GetSupportedArchitectureAtIndex (uint32_t idx, ArchSpec &arch)
 {
     ArchSpec remote_arch = m_gdb_client.GetSystemArchitecture();
 
-    // TODO: 64 bit systems should also advertize support for 32 bit arch
-    // unknown CPU, we just support the one arch
     if (idx == 0)
     {
         arch = remote_arch;
         return true;
     }
+    else if (idx == 1 &&
+            remote_arch.GetTriple().isOSLinux() &&
+            remote_arch.GetTriple().isArch64Bit())
+    {
+        arch.SetTriple("i686-linux-gnu");
+        return true;
+    }
     return false;
 }
 
 size_t
 PlatformRemoteGDBServer::GetSoftwareBreakpointTrapOpcode (Target &target, BreakpointSite *bp_site)
 {
     // This isn't needed if the z/Z packets are supported in the GDB remote
     // server. But we might need a packet to detect this.

source/Plugins/Process/Utility/RegisterContextLinux_i386.cpp

RegisterContextLinux_i386::GetGPRSize() const
     return sizeof(GPR);
 }
 
 const RegisterInfo *
 RegisterContextLinux_i386::GetRegisterInfo() const
 {
     switch (m_target_arch.GetMachine())
     {
         case llvm::Triple::x86:            
             return g_register_infos_i386;
+        case llvm::Triple::x86_64:
+            return g_register_infos_i386;
         default:
             assert(false && "Unhandled target architecture.");
             return NULL;
     }
 }
 
 uint32_t
 RegisterContextLinux_i386::GetRegisterCount () const