Add initial *-*-rtems* target, from Joel Sherrill

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@134283 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/InitHeaderSearch.cpp b/lib/Frontend/InitHeaderSearch.cpp
index 1bd7f8f..85e30f8 100644
--- a/lib/Frontend/InitHeaderSearch.cpp
+++ b/lib/Frontend/InitHeaderSearch.cpp
@@ -553,6 +553,8 @@
     AddPath("/boot/develop/headers/posix", System, true, false, false);
     AddPath("/boot/develop/headers",  System, true, false, false);
     break;
+  case llvm::Triple::RTEMS:
+    break;
   case llvm::Triple::Cygwin:
     AddPath("/usr/include/w32api", System, true, false, false);
     break;
@@ -590,7 +592,8 @@
     break;
   }
 
-  AddPath("/usr/include", System, false, false, false);
+  if ( os != llvm::Triple::RTEMS )
+    AddPath("/usr/include", System, false, false, false);
 }
 
 void InitHeaderSearch::