Reland r206934 with a hopefully fixed test

llvm-svn: 207155

clang/lib/Driver/WindowsToolChain.cpp

@@ -293,7 +293,6 @@ void Windows::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
   if (DriverArgs.hasArg(options::OPT_nostdlibinc))
     return;
 
-#ifdef _MSC_VER
   // Honor %INCLUDE%. It should know essential search paths with vcvarsall.bat.
   if (const char *cl_include_dir = getenv("INCLUDE")) {
     SmallVector<StringRef, 8> Dirs;
@@ -305,6 +304,7 @@ void Windows::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
       return;
   }
 
+#ifdef _MSC_VER
   std::string VSDir;
   std::string WindowsSDKDir;
 

clang/test/Driver/windows-include-env.c

@@ -0,0 +1,4 @@
+// RUN: env INCLUDE=my_system_headers %clang --target=i686-windows -c %s -### 2>&1 | FileCheck %s
+// RUN: env INCLUDE=my_system_headers %clang_cl -c %s -### 2>&1 | FileCheck %s
+// CHECK: "-cc1"
+// CHECK: "-internal-isystem" "my_system_headers"