This fixes the Builtins-sparc-linux testsuite failures on Linux
SPARC which occur because clang cannot find the 32-bit runtime
libraries when -m32 is passed on the command line. The same
workaround is already being used on X86 and PPC.
Also, switch the CHECK-DEBIAN-SPARC tests to use debian_multiarch_tree
as both sparc and sparc64 are using the MultiArch mechanism on modern Debian
systems the same way as x86_64, powerpc64el and others. Thus, switch the
CHECK-DEBIAN-SPARC32 and CHECK-DEBIAN-SPARC64 tests to use the files from
the debian_multiarch_tree directory for the header and linker path tests.
Finally, rename CHECK-DEBIAN-SPARC32 to CHECK-DEBIAN-SPARC to match the naming
scheme of the Debian MultiArch checks for the other Debian architectures.