[llvm] [runtimes] Skip custom linker validation for gpu/offload targets (PR #189933)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-mlir-rhel-clang` running on `ppc64le-mlir-rhel-test` while building `llvm` at step 6 "test-build-check-mlir-build-only-check-mlir".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/129/builds/42067

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

```
Step 6 (test-build-check-mlir-build-only-check-mlir) failure: 1200 seconds without output running [b'ninja', b'check-mlir'], attempting to kill
...
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/88/180 (4005 of 4014)
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/90/180 (4006 of 4014)
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/9/180 (4007 of 4014)
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/97/180 (4008 of 4014)
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/98/180 (4009 of 4014)
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/94/180 (4010 of 4014)
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/99/180 (4011 of 4014)
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/89/180 (4012 of 4014)
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/95/180 (4013 of 4014)
PASS: MLIR-Unit :: Analysis/Presburger/./MLIRPresburgerTests/96/180 (4014 of 4014)
command timed out: 1200 seconds without output running [b'ninja', b'check-mlir'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=3479.424913

```

</details>

https://github.com/llvm/llvm-project/pull/189933