This patch adds an option (no-clang-tools) to disable building clang-tools-extra when
performing release testing. Prior to this patch, clang-tools-extra was built by default,
but on some platforms (such as AIX), clang-tools-extra is not supported, and so we do
not normally build it. Furthermore, this change should not change the invocation for
targets that build clang-tools-extra normally.
Differential Revision: https://reviews.llvm.org/D119520
db691903d2