[tests][go]Add -stdlib=libc++ to build GO test if LLVM is built with libc++

[xingxue]

Summary

When libc++ is used to build LLVM libraries, these libraries have dependencies on libc++ and C++ STL signatures in these libraries are corresponding to libc++ implementation. Therefore, -stdlib=libc++ is required on the C++ compiler command for building GO tests that link with these LLVM libraries.

[sfertile]

LGTM.

[hubert.reinterpretcast]

llvm/tools/llvm-go/llvm-go.go

98 ↗

(On Diff #199442)

The added lines use spaces in place of the tabs used on the other lines.

[xingxue]

llvm/tools/llvm-go/llvm-go.go

98 ↗

(On Diff #199442)

Thanks for spotting this. Changed to use tabs.

llvm/trunk/tools/llvm-go/llvm-go.go

func llvmConfig(args ...string) string {
   outstr = strings.TrimSuffix(outstr, "\n")
   outstr = strings.Replace(outstr, "\n", " ", -1)
   return outstr
 }
 
 func llvmFlags() compilerFlags {
   args := append([]string{"--ldflags", "--libs", "--system-libs"}, components...)
   ldflags := llvmConfig(args...)
+  stdLibOption := ""
+  if strings.Contains(llvmConfig("--cxxflags"), "-stdlib=libc++") {
+    // If libc++ is used to build LLVM libraries, -stdlib=libc++ is
+    // needed to resolve dependent symbols
+    stdLibOption = "-stdlib=libc++"
+  }
   if runtime.GOOS != "darwin" {
     // OS X doesn't like -rpath with cgo. See:
     // https://github.com/golang/go/issues/7293
     ldflags = "-Wl,-rpath," + llvmConfig("--libdir") + " " + ldflags
   }
   return compilerFlags{
     cpp: llvmConfig("--cppflags"),
-    cxx: "-std=c++11",
+    cxx: "-std=c++11" + " " + stdLibOption,
     ld:  ldflags,
   }
 }
 
 func addTag(args []string, tag string) []string {
   args = append([]string{}, args...)
   addedTag := false
   for i, a := range args {