Factor out GetEnvDeveloperDir() (NFC)

lldb/source/Host/macosx/objcxx/HostInfoMacOSX.mm

 #else
       arch_32.GetTriple().setOS(llvm::Triple::IOS);
 #endif
       arch_64.Clear();
     }
   }
 }
 
+/// Return and cache $DEVELOPER_DIR if it is set and exists.
+static std::string GetEnvDeveloperDir() {
+  static std::string g_env_developer_dir;
+  static std::once_flag g_once_flag;
+  std::call_once(g_once_flag, [&]() {
+    if (const char *developer_dir_env_var = getenv("DEVELOPER_DIR")) {
+      FileSpec fspec(developer_dir_env_var);
+      if (FileSystem::Instance().Exists(fspec))
+        g_env_developer_dir = fspec.GetPath();
+    }});
+  return g_env_developer_dir;
+}
+
 FileSpec HostInfoMacOSX::GetXcodeContentsDirectory() {
   static FileSpec g_xcode_contents_path;
   static std::once_flag g_once_flag;
   std::call_once(g_once_flag, [&]() {
     // Try the shlib dir first.
     if (FileSpec fspec = HostInfo::GetShlibDir()) {
       if (FileSystem::Instance().Exists(fspec)) {
         std::string xcode_contents_dir =
             XcodeSDK::FindXcodeContentsDirectoryInPath(fspec.GetPath());
         if (!xcode_contents_dir.empty()) {
           g_xcode_contents_path = FileSpec(xcode_contents_dir);
           return;
         }
       }
     }
 
-    if (const char *developer_dir_env_var = getenv("DEVELOPER_DIR")) {
-      FileSpec fspec(developer_dir_env_var);
-      if (FileSystem::Instance().Exists(fspec)) {
-        // FIXME: This looks like it couldn't possibly work!
-        std::string xcode_contents_dir =
-            XcodeSDK::FindXcodeContentsDirectoryInPath(fspec.GetPath());
-        if (!xcode_contents_dir.empty()) {
-          g_xcode_contents_path = FileSpec(xcode_contents_dir);
-          return;
-        }
-      }
-    }
+    std::string env_developer_dir = GetEnvDeveloperDir();
+    if (!env_developer_dir.empty()) {
+          XcodeSDK::FindXcodeContentsDirectoryInPath(env_developer_dir);
 
     FileSpec fspec(HostInfo::GetXcodeSDKPath(XcodeSDK::GetAnyMacOS()));
     if (fspec) {
       if (FileSystem::Instance().Exists(fspec)) {
         std::string xcode_contents_dir =
             XcodeSDK::FindXcodeContentsDirectoryInPath(fspec.GetPath());
         if (!xcode_contents_dir.empty()) {
           g_xcode_contents_path = FileSpec(xcode_contents_dir);
lldb_private::FileSpec HostInfoMacOSX::GetXcodeDeveloperDirectory() {
   return g_developer_directory;
 }
 
 static std::string GetXcodeSDK(XcodeSDK sdk) {
   XcodeSDK::Info info = sdk.Parse();
   std::string sdk_name = XcodeSDK::GetCanonicalName(info);
   auto find_sdk = [](std::string sdk_name) -> std::string {
     std::string xcrun_cmd;
-    Environment env = Host::GetEnvironment();
-    std::string developer_dir = env.lookup("DEVELOPER_DIR");
+    std::string developer_dir = GetEnvDeveloperDir();
     if (developer_dir.empty())
       if (FileSpec fspec = HostInfo::GetShlibDir())
         if (FileSystem::Instance().Exists(fspec)) {
           FileSpec path(
               XcodeSDK::FindXcodeContentsDirectoryInPath(fspec.GetPath()));
           if (path.RemoveLastPathComponent())
             developer_dir = path.GetPath();
         }