[llvm] [llvm-mc-assemble-fuzzer] Fix Triple passing (PR #181135)

[Tomer Shafir via llvm-commits]

tomershafir wrote:

Seems not, I agree its problematic and we should cover this configuration (`-DLLVM_USE_SANITIZER=Address -DLLVM_USE_SANITIZE_COVERAGE=On`)

https://github.com/llvm/llvm-project/pull/181135