compiler-rt/test: Clean up Android specific workarounds in lit.common.cfg.

-pie -Wl,--enable-new-dtags are no longer needed because
the driver passes them by default as of r316606.

Prepend -fuse-ld=gold instead of appending it so that the linker can
be overridden using COMPILER_RT_TEST_COMPILER_CFLAGS.

Differential Revision: https://reviews.llvm.org/D56697

llvm-svn: 351252