We now have a cmake option to change the default: ENABLE_LINKER_BUILD_ID.

The reason is that build-id is fairly expensive, so we shouldn't impose
it in the regular edit/build cycle.

This is similar to gcc, that has an off by default --enable-linker-build-id
option.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@271692 91177308-0d34-0410-b5e6-96231b3b80d8