[llvm] [LTO] Fix a crash with thin LTO caching and asm output (PR #138203)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ml-opt-devrel-x86-64` running on `ml-opt-devrel-x86-64-b2` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/175/builds/18505

<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 :: ThinLTO/X86/cache-emit-asm.ll' FAILED ********************
Exit Code: 127

Command Output (stderr):
--
rm -rf /b/ml-opt-devrel-x86-64-b1/build/test/ThinLTO/X86/Output/cache-emit-asm.ll.tmp.cache # RUN: at line 5
+ rm -rf /b/ml-opt-devrel-x86-64-b1/build/test/ThinLTO/X86/Output/cache-emit-asm.ll.tmp.cache
/b/ml-opt-devrel-x86-64-b1/build/bin/opt -module-hash -module-summary -thinlto-bc /b/ml-opt-devrel-x86-64-b1/llvm-project/llvm/test/ThinLTO/X86/cache-emit-asm.ll -o /b/ml-opt-devrel-x86-64-b1/build/test/ThinLTO/X86/Output/cache-emit-asm.ll.tmp1.bc # RUN: at line 6
+ /b/ml-opt-devrel-x86-64-b1/build/bin/opt -module-hash -module-summary -thinlto-bc /b/ml-opt-devrel-x86-64-b1/llvm-project/llvm/test/ThinLTO/X86/cache-emit-asm.ll -o /b/ml-opt-devrel-x86-64-b1/build/test/ThinLTO/X86/Output/cache-emit-asm.ll.tmp1.bc
ld.lld --thinlto-cache-dir=/b/ml-opt-devrel-x86-64-b1/build/test/ThinLTO/X86/Output/cache-emit-asm.ll.tmp.cache --lto-emit-asm /b/ml-opt-devrel-x86-64-b1/build/test/ThinLTO/X86/Output/cache-emit-asm.ll.tmp1.bc # RUN: at line 7
+ ld.lld --thinlto-cache-dir=/b/ml-opt-devrel-x86-64-b1/build/test/ThinLTO/X86/Output/cache-emit-asm.ll.tmp.cache --lto-emit-asm /b/ml-opt-devrel-x86-64-b1/build/test/ThinLTO/X86/Output/cache-emit-asm.ll.tmp1.bc
/b/ml-opt-devrel-x86-64-b1/build/test/ThinLTO/X86/Output/cache-emit-asm.ll.script: line 3: ld.lld: command not found

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/138203