[RISCV] Fix test failures on non-assert builds introduced in r322494

Thanks to Eli Friedman, who suggested the reason these tests failed on a few 
buildbots yet works fine locally is because non-assert builds don't emit value 
labels.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@322514 91177308-0d34-0410-b5e6-96231b3b80d8