Basic: Add support for a build variable to set the repository path that goes
into the Clang version.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@128595 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Makefile b/Makefile
index 1216dad..b6c630a 100644
--- a/Makefile
+++ b/Makefile
@@ -46,6 +46,9 @@
 ifdef CLANG_VENDOR
 CPP.Flags += -DCLANG_VENDOR='"$(CLANG_VENDOR) "'
 endif
+ifdef CLANG_REPOSITORY_STRING
+CPP.Flags += -DCLANG_REPOSITORY_STRING='"$(CLANG_REPOSITORY_STRING)"'
+endif
 
 # Disable -fstrict-aliasing. Darwin disables it by default (and LLVM doesn't
 # work with it enabled with GCC), Clang/llvm-gcc don't support it yet, and newer