scan-build: Set CC and CXX as make variables when wrapping make builds.

Variables set in a makefile are not overridden by environment variables.
Make sure we actually override CC and CXX when using scan-build.

Patch by Steve McCoy!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk/tools/scan-build@189372 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed