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

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.

Reviewers: hubert.reinterpretcast, sfertile, amyk, EricWF

Reviewed By: sfertile, hubert.reinterpretcast

Subscribers: jsji, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61900

llvm-svn: 360895

tools/llvm-go/llvm-go.go

@@ -90,6 +90,12 @@ func llvmConfig(args ...string) string {
 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
@@ -97,7 +103,7 @@ func llvmFlags() compilerFlags {
 	}
 	return compilerFlags{
 		cpp: llvmConfig("--cppflags"),
-		cxx: "-std=c++11",
+		cxx: "-std=c++11" + " " + stdLibOption,
 		ld:  ldflags,
 	}
 }