The runtimes build expects libclang_rt.tysan.a to be available, but the
check-tysan target does not actually depend on it when built using a
runtimes build with LLVM_ENABLE_RUNTIMES pointing at ./llvm. This means
we get test failures when running check-compiler-rt due to the missing
static archive.
This patch also makes check-tysan depend on tysan when we are using the
runtimes build.
This is causing premerge failures currently since we recently migrated
to the runtimes build.