[clang] [OpenCL] Fix extensions checks for 3.1 (PR #208370)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-x86_64-linux-abi-test` running on `sie-linux-worker2` while building `clang` at step 6 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/8/builds/32359

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

```
Step 6 (build-unified-tree) failure: build (failure)
...
1580.027 [1444/10/6362] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/AST/ASTDumperTest.cpp.o
1585.783 [1443/10/6363] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/AST/ASTExprTest.cpp.o
1585.940 [1442/10/6364] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/ASTMatchers/ASTMatchersNodeTest.cpp.o
1587.999 [1441/10/6365] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/AST/ASTImporterFixtures.cpp.o
1588.064 [1440/10/6366] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/AST/ASTVectorTest.cpp.o
1589.646 [1439/10/6367] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/AST/ASTImporterObjCTest.cpp.o
1589.704 [1438/10/6368] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/AST/CommentLexer.cpp.o
1589.769 [1437/10/6369] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/AST/CommentParser.cpp.o
1589.804 [1436/10/6370] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/AST/CommentTextTest.cpp.o
1598.150 [1435/10/6371] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/ASTMatchers/ASTMatchersNarrowingTest.cpp.o
command timed out: 1200 seconds without output running [b'ninja'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=2869.850266

```

</details>

https://github.com/llvm/llvm-project/pull/208370