Add support for building with _GLIBCXX_DEBUG.  New configure option
--enable-expensive-checks allows the developer to enable runtime
checking that can greatly increase compile time.  Currently it only
turns on _GLIBCXX_DEBUG.  Other expensive debugging checks added later
should be controlled by this configure option.

This patch also updates llvm-config with a --cppflags option to inform
llvm-gcc how to build itself so that it is compatible with an llvm that
was built with _GLIBCXX_DEBUG.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37777 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-config/Makefile b/tools/llvm-config/Makefile
index 471b5bc..5ceef2e 100644
--- a/tools/llvm-config/Makefile
+++ b/tools/llvm-config/Makefile
@@ -20,6 +20,7 @@
 ifeq ($(HAVE_PERL),1)
 
 # Combine preprocessor flags (except for -I) and CXX flags.
+SUB_CPPFLAGS = ${CPP.Defines}
 SUB_CFLAGS = ${CPP.BaseFlags} ${C.Flags}
 SUB_CXXFLAGS = ${CPP.BaseFlags} ${CXX.Flags}
 
@@ -56,7 +57,8 @@
 # Build our final script.
 $(ToolDir)/llvm-config: llvm-config.in $(FinalLibDeps)
 	$(Echo) "Building llvm-config script."
-	$(Verb) $(ECHO) 's,@LLVM_CFLAGS@,$(SUB_CFLAGS),' > temp.sed
+	$(Verb) $(ECHO) 's,@LLVM_CPPFLAGS@,$(SUB_CPPFLAGS),' > temp.sed
+	$(Verb) $(ECHO) 's,@LLVM_CFLAGS@,$(SUB_CFLAGS),' >> temp.sed
 	$(Verb) $(ECHO) 's,@LLVM_CXXFLAGS@,$(SUB_CXXFLAGS),' >> temp.sed
 	$(Verb) $(ECHO) 's,@LLVM_LDFLAGS@,$(SUB_LDFLAGS),' >> temp.sed
 	$(Verb) $(ECHO) 's,@LLVM_BUILDMODE@,$(BuildMode),' >> temp.sed