[AIX][llvm-go] AIX linker does not recognize `-rpath`

[stevewan]

Summary

The existing logic adds -rpath to CGO_LDFLAGS, which is not a valid linker option on AIX. This patch substitutes it with -blibpath on AIX.

[daltenty]

LGTM, with minor nit

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

106

nit: an if-elseif would be cleaner than the nested if here:
if runtime.GOOS == "aix" {
...
}
else if runtime.GOOS != "darwin" {
...
}

[stevewan]

Flatten nested if

[stevewan]

Fix formatting

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

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" {
+  if runtime.GOOS == "aix" {
+    // AIX linker does not honour `-rpath`, the closest substitution
+    // is `-blibpath`
+    ldflags = "-Wl,-blibpath:" + llvmConfig("--libdir") + " " + ldflags
+  } else 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++14" + " " + stdLibOption,
     ld:  ldflags,
   }
 }