Define _GNU_SOURCE for RTEMS c++

Summary: This is required by the libc++ locale support.

Reviewers: jyknight

Subscribers: fedor.sergeev

Differential Revision: https://reviews.llvm.org/D36121

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@309815 91177308-0d34-0410-b5e6-96231b3b80d8

Author: googlewalt

lib/Basic/Targets/OSTargets.h

@@ -505,6 +505,8 @@ class LLVM_LIBRARY_VISIBILITY RTEMSTargetInfo : public OSTargetInfo<Target> {
 
     Builder.defineMacro("__rtems__");
     Builder.defineMacro("__ELF__");
+    if (Opts.CPlusPlus)
+      Builder.defineMacro("_GNU_SOURCE");
   }
 
 public:

test/Preprocessor/init.c

@@ -8955,6 +8955,7 @@
 // KFREEBSDI686-DEFINE:#define __GLIBC__ 1
 //
 // RUN: %clang_cc1 -x c++ -triple i686-pc-linux-gnu -fobjc-runtime=gcc -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GNUSOURCE %s
+// RUN: %clang_cc1 -x c++ -triple sparc-rtems-elf -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GNUSOURCE %s
 // GNUSOURCE:#define _GNU_SOURCE 1
 //
 // RUN: %clang_cc1 -x c++ -std=c++98 -fno-rtti -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix NORTTI %s