[llvm] [llvm-debuginfo-analyzer] Fix crash with WebAssembly dead code (PR #141616)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-sie-ubuntu-fast` running on `sie-linux-worker` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/28570

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: tools/llvm-debuginfo-analyzer/WebAssembly/wasm-32bit-tombstone.s' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/llvm-mc -arch=wasm32 -filetype=obj                /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/test/tools/llvm-debuginfo-analyzer/WebAssembly/wasm-32bit-tombstone.s                 -o /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/test/tools/llvm-debuginfo-analyzer/WebAssembly/Output/wasm-32bit-tombstone.s.tmp.wasm-32bit-tombstone.wasm # RUN: at line 27
+ /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/llvm-mc -arch=wasm32 -filetype=obj /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/test/tools/llvm-debuginfo-analyzer/WebAssembly/wasm-32bit-tombstone.s -o /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/test/tools/llvm-debuginfo-analyzer/WebAssembly/Output/wasm-32bit-tombstone.s.tmp.wasm-32bit-tombstone.wasm
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/llvm-mc: error: invalid target 'wasm32'.
--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/141616