[libclc] libclc: increase fp16 support (PR #98149)

[Michał Górny via cfe-commits]

mgorny wrote:

This change seems to have caused test regression. This is Gentoo Linux amd64, tried LLVM 72d8c2737bb557af9d0c735b9fa30b1b03485627 and 18.1.8.

To reproduce, I've done:

```
cmake -G Ninja "${llvm_project}"/libclc -DLIBCLC_TARGETS_TO_BUILD="spirv-mesa3d-;spirv64-mesa3d-;r600--;amdgcn--;amdgcn-mesa-mesa3d;amdgcn--amdhsa"
ninja
ninja test
```

The result:

```
[0/1] Running tests...
Test project /home/mgorny/git/llvm-project/libclc/build
    Start 1: external-calls-tahiti-amdgcn--.bc
1/7 Test #1: external-calls-tahiti-amdgcn--.bc .............***Failed    5.46 sec
    Start 2: external-calls-amdgcn--amdhsa.bc
2/7 Test #2: external-calls-amdgcn--amdhsa.bc ..............***Failed    5.54 sec
    Start 3: external-calls-tahiti-amdgcn-mesa-mesa3d.bc
3/7 Test #3: external-calls-tahiti-amdgcn-mesa-mesa3d.bc ...***Failed    5.43 sec
    Start 4: external-calls-cedar-r600--.bc
4/7 Test #4: external-calls-cedar-r600--.bc ................   Passed    2.05 sec
    Start 5: external-calls-cypress-r600--.bc
5/7 Test #5: external-calls-cypress-r600--.bc ..............   Passed    2.07 sec
    Start 6: external-calls-barts-r600--.bc
6/7 Test #6: external-calls-barts-r600--.bc ................   Passed    2.03 sec
    Start 7: external-calls-cayman-r600--.bc
7/7 Test #7: external-calls-cayman-r600--.bc ...............   Passed    2.07 sec

57% tests passed, 3 tests failed out of 7

Total Test time (real) =  24.66 sec

The following tests FAILED:
	  1 - external-calls-tahiti-amdgcn--.bc (Failed)
	  2 - external-calls-amdgcn--amdhsa.bc (Failed)
	  3 - external-calls-tahiti-amdgcn-mesa-mesa3d.bc (Failed)
Errors while running CTest
Output from these tests are in: /home/mgorny/git/llvm-project/libclc/build/Testing/Temporary/LastTest.log
Use "--rerun-failed --output-on-failure" to re-run the failed cases verbosely.
FAILED: CMakeFiles/test.util 
cd /home/mgorny/git/llvm-project/libclc/build && /usr/bin/ctest --force-new-ctest-process
ninja: build stopped: subcommand failed.
```

LastTest.log: [LastTest.log](https://github.com/user-attachments/files/16320006/LastTest.log)

If I go back to 6838c7afb2d2fa5eb642a4b5922ae55d97f7b344, they all pass.

https://github.com/llvm/llvm-project/pull/98149