[clang] [llvm] [Hexagon] Add V81 support to compiler and assembler (PR #164922)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

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

Full details are available at: https://lab.llvm.org/buildbot/#/builders/157/builds/41837

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

```
Step 6 (test-build-unified-tree-check-flang) failure: 1200 seconds without output running [b'ninja', b'check-flang'], attempting to kill
...
357.709 [2/8/24] Building CXX object tools/flang/unittests/Optimizer/CMakeFiles/FlangOptimizerTests.dir/FIRTypesTest.cpp.o
374.720 [2/7/25] Building CXX object tools/flang/unittests/Optimizer/CMakeFiles/FlangOptimizerTests.dir/Builder/Runtime/IntrinsicsTest.cpp.o
376.202 [2/6/26] Building CXX object tools/flang/unittests/Optimizer/CMakeFiles/FlangOptimizerTests.dir/Builder/Runtime/DerivedTest.cpp.o
385.863 [2/5/27] Building CXX object tools/flang/unittests/Optimizer/CMakeFiles/FlangOptimizerTests.dir/Builder/Runtime/CommandTest.cpp.o
387.462 [2/4/28] Building CXX object tools/flang/unittests/Optimizer/CMakeFiles/FlangOptimizerTests.dir/Builder/Runtime/AssignTest.cpp.o
395.952 [2/3/29] Building CXX object tools/flang/unittests/Optimizer/CMakeFiles/FlangOptimizerTests.dir/Builder/ComplexTest.cpp.o
409.341 [2/2/30] Building CXX object tools/flang/unittests/Optimizer/CMakeFiles/FlangOptimizerTests.dir/Builder/Runtime/AllocatableTest.cpp.o
419.823 [2/1/31] Building CXX object tools/flang/unittests/Optimizer/CMakeFiles/FlangOptimizerTests.dir/Builder/Runtime/RaggedTest.cpp.o
425.734 [1/1/32] Linking CXX executable tools/flang/unittests/Optimizer/FlangOptimizerTests
425.734 [0/1/32] Running the Flang regression tests
command timed out: 1200 seconds without output running [b'ninja', b'check-flang'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=1626.535478

```

</details>

https://github.com/llvm/llvm-project/pull/164922