[Driver][Gnu] Support -nolibc flag This can be used to disable libc linking. This flag is supported by GCC since version 9 as well as some Clang target toolchains. Differential Revision: https://reviews.llvm.org/D58326 git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@354210 91177308-0d34-0410-b5e6-96231b3b80d8