[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-win` running on `sie-win-worker` while building `llvm` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/46/builds/19044

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

```
Step 7 (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 (stdout):
--
# RUN: at line 27
z:\b\llvm-clang-x86_64-sie-win\build\bin\llvm-mc.exe -arch=wasm32 -filetype=obj                Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\tools\llvm-debuginfo-analyzer\WebAssembly/wasm-32bit-tombstone.s                 -o Z:\b\llvm-clang-x86_64-sie-win\build\test\tools\llvm-debuginfo-analyzer\WebAssembly\Output\wasm-32bit-tombstone.s.tmp.wasm-32bit-tombstone.wasm
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\llvm-mc.exe' -arch=wasm32 -filetype=obj 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\tools\llvm-debuginfo-analyzer\WebAssembly/wasm-32bit-tombstone.s' -o 'Z:\b\llvm-clang-x86_64-sie-win\build\test\tools\llvm-debuginfo-analyzer\WebAssembly\Output\wasm-32bit-tombstone.s.tmp.wasm-32bit-tombstone.wasm'
# .---command stderr------------
# | z:\b\llvm-clang-x86_64-sie-win\build\bin\llvm-mc.exe: error: invalid target 'wasm32'.
# `-----------------------------
# error: command failed with exit status: 1

--

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


```

</details>

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