[llvm] [LLVM] Fix not passing CMAKE_CROSSCOMPILING_EMULATOR for amdgpu (PR #209828)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-test-suite` running on `ppc64le-clang-test-suite` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/95/builds/21539

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

```
Step 6 (test-build-unified-tree-check-all) failure: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
...
600.447 [1/9/1473] Linking CXX executable unittests/MIR/MIRTests
600.480 [1/8/1474] Linking CXX executable unittests/Remarks/RemarksTests
600.480 [1/7/1475] Linking CXX executable unittests/tools/llvm-cfi-verify/CFIVerifyTests
600.634 [1/6/1476] Linking CXX executable unittests/MC/MCTests
600.680 [1/5/1477] Linking CXX executable bin/OrcV2CBindingsAddObjectFile
600.681 [1/4/1478] Linking CXX executable unittests/Transforms/Instrumentation/InstrumentationTests
600.707 [1/3/1479] Linking CXX executable bin/OrcV2CBindingsVeryLazy
600.776 [1/2/1480] Linking CXX executable tools/clang/tools/extra/include-cleaner/unittests/ClangIncludeCleanerTests
618.608 [1/1/1481] Linking CXX executable tools/clang/unittests/AllClangUnitTests
618.609 [0/1/1481] Running all regression tests
command timed out: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=1819.541436

```

</details>

https://github.com/llvm/llvm-project/pull/209828