Reviewer for a small clang Driver code change needed

Hi!

I have made a small change to the clang Driver code [1] which fixes the testsuite
on Linux/sparc64

Currently, more than 400 tests fail on Linux/sparc64 [2] which drops to around 70
failures with the fix applied.

The reason for that is that without the fix, all 32-bit tests will fail on 64-bit
Linux/sparc64 since clang is unable to find the 32-bit shared libraries on the
64-bit system.

What this fix does is actually changing the Linux/sparc64 Driver code to use the
same Debian MultiArch tests and library paths as they are already used for x86
and PowerPC, hence we're actually not introducing anything new, just make SPARC
behave the same as x86 and PowerPC.

The Debian Multilib test that this change replace also make no sense since there
was never a Debian 8 release for sparc. The last official Debian sparc release
was version 7.10 (Debian Wheezy).

After that, Debian/sparc64 has been the only SPARC port in Debian - although this
change will not break the 32-bit Debian/sparc port as sparc and sparc64 use MultiArch
the same way on Debian as x86 and PowerPC do.

So, could someone review and commit that change for me so we can reduce the number
of testsuite failures on Linux/sparc64?

Thanks,
Adrian