[clang] [Clang] Include LLVM libc header directory from Linux (PR #175593)

[Petr Hosek via cfe-commits]

================
@@ -747,6 +747,13 @@ void Linux::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
   if (DriverArgs.hasArg(options::OPT_nostdlibinc))
     return;
 
+  // The LLVM-libc environment stores its C headers in the Clang include
+  // directory.
+  if (getTriple().getEnvironment() == llvm::Triple::LLVM) {
----------------
petrhosek wrote:

Is there a reason why we couldn't do this unconditionally?

https://github.com/llvm/llvm-project/pull/175593