[CUDA] "Support" ASAN arguments in CudaToolChain

This fixes a bug that was introduced in rL287285. The bug made it
illegal to pass -fsanitize=address during CUDA compilation because the
CudaToolChain class was switched from deriving from the Linux toolchain
class to deriving directly from the ToolChain toolchain class. When
CudaToolChain derived from Linux, it used Linux's getSupportedSanitizers
method, and that method allowed ASAN, but when it switched to deriving
directly from ToolChain, it inherited a getSupportedSanitizers method
that didn't allow for ASAN.

This patch fixes that bug by creating a getSupportedSanitizers method
for CudaToolChain that supports ASAN.

This patch also fixes the test that checks that -fsanitize=address is
passed correctly for CUDA builds. That test didn't used to notice if an
error message was emitted, and that's why it didn't catch this bug when
it was first introduced. With the fix from this patch, that test will
now catch any similar bug in the future.

llvm-svn: 288448