Use gmake on FreeBSD lldb builder; temporarily relax the warnings level for lld builder on FreeBSD due the open bug 17788 - clang -pedantic -Werror complains about C11 Generics in math.h.

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@214597 91177308-0d34-0410-b5e6-96231b3b80d8