Allow LLDB to be built on a system with an installed gcc/g++ that isn't the...

Allow LLDB to be built on a system with an installed gcc/g++ that isn't the default. I recently installed gcc-4.7/g++-4.7 on Ubuntu and tried to build by specifying:

CC=gcc-4.7 CXX=g++-4.7

as configure and make args, but it didn't work when being run with makefiles. This patch fixes that.

llvm-svn: 182158