[Driver] move ELFIAMCU / RTEMS header search path management to the driver

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D158132

Author: brad0

clang/lib/Lex/InitHeaderSearch.cpp

@@ -231,8 +231,6 @@ void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
 
   if (HSOpts.UseStandardSystemIncludes) {
     switch (os) {
-    case llvm::Triple::ELFIAMCU:
-      break;
     case llvm::Triple::Win32:
       if (triple.getEnvironment() != llvm::Triple::Cygnus)
         break;
@@ -270,8 +268,6 @@ void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
   }
 
   switch (os) {
-  case llvm::Triple::RTEMS:
-    break;
   case llvm::Triple::Win32:
     switch (triple.getEnvironment()) {
     default: llvm_unreachable("Include management is handled in the driver.");
@@ -286,14 +282,7 @@ void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
     break;
   }
 
-  switch (os) {
-  case llvm::Triple::RTEMS:
-  case llvm::Triple::ELFIAMCU:
-    break;
-  default:
-    AddPath("/usr/include", ExternCSystem, false);
-    break;
-  }
+  AddPath("/usr/include", ExternCSystem, false);
 }
 
 void InitHeaderSearch::AddDefaultCPlusPlusIncludePaths(
@@ -330,6 +319,7 @@ bool InitHeaderSearch::ShouldAddDefaultIncludePaths(
     const llvm::Triple &triple) {
   switch (triple.getOS()) {
   case llvm::Triple::AIX:
+  case llvm::Triple::ELFIAMCU:
   case llvm::Triple::Emscripten:
   case llvm::Triple::FreeBSD:
   case llvm::Triple::Fuchsia:
@@ -342,6 +332,7 @@ bool InitHeaderSearch::ShouldAddDefaultIncludePaths(
   case llvm::Triple::OpenBSD:
   case llvm::Triple::PS4:
   case llvm::Triple::PS5:
+  case llvm::Triple::RTEMS:
   case llvm::Triple::Solaris:
   case llvm::Triple::WASI:
   case llvm::Triple::ZOS: