[x86] Exclusion of incorrect include headers paths for MCU target

[andreybokhanko]

Summary

This patch excludes incorrect include headers paths for MCU target.

[mkuper]

LGTM

lib/Frontend/InitHeaderSearch.cpp

if (HSOpts.UseStandardSystemIncludes) {
     switch (os) {
     case llvm::Triple::CloudABI:
     case llvm::Triple::FreeBSD:
     case llvm::Triple::NetBSD:
     case llvm::Triple::OpenBSD:
     case llvm::Triple::Bitrig:
     case llvm::Triple::NaCl:
     case llvm::Triple::PS4:
+    case llvm::Triple::ELFIAMCU:
       break;
     case llvm::Triple::Win32:
       if (triple.getEnvironment() != llvm::Triple::Cygnus)
         break;
     default:
       // FIXME: temporary hack: hard-coded paths.
       AddPath("/usr/local/include", System, false);
       break;
void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
   default:
     break;
   }
 
   switch (os) {
   case llvm::Triple::CloudABI:
   case llvm::Triple::RTEMS:
   case llvm::Triple::NaCl:
+  case llvm::Triple::ELFIAMCU:
     break;
   case llvm::Triple::PS4: {
     // <isysroot> gets prepended later in AddPath().
     std::string BaseSDKPath = "";
     if (!HasSysroot) {
       const char *envValue = getenv("SCE_PS4_SDK_DIR");
       if (envValue)
         BaseSDKPath = envValue;

test/Driver/elfiamcu-header-search.c

+// REQUIRES: x86-registered-target
+
+// RUN: %clang -target i386-pc-elfiamcu -c -v %s 2>&1 | FileCheck %s
+// CHECK-NOT: /usr/include
+// CHECK-NOT: /usr/local/include
+