Revert "Revert "Don't use unique section names by default if using the integrated as.""

This reverts commit r233398, bringing back 233393 now that LLVM is fixed.

Original message:

Don't use unique section names by default if using the integrated as.

This saves some IO and ccache space by not creating long section names. It
should work with every ELF linker.

llvm-svn: 234101