[clang] [libc] [llvm] [clang] Make __builtin_exp and __builtin_expf constexpr. (PR #199808)

[via cfe-commits]

lntue wrote:

> Tests still fail though?

@tbaederr : The only failing test in the CI is lldb-api:
```
2026-07-17T04:52:35.1561285Z ********************
2026-07-17T04:52:35.1561524Z Unresolved Tests (1):
2026-07-17T04:52:35.1561830Z   lldb-api :: commands/gui/spawn-threads/TestGuiSpawnThreads.py
2026-07-17T04:52:35.1562081Z 
2026-07-17T04:52:35.1562086Z 
2026-07-17T04:52:35.1562172Z Testing Time: 67.58s
2026-07-17T04:52:35.1562296Z 
2026-07-17T04:52:35.1562398Z Total Discovered Tests: 34593
2026-07-17T04:52:35.1562639Z   Skipped          :     2 (0.01%)
2026-07-17T04:52:35.1562883Z   Unsupported      :   500 (1.45%)
2026-07-17T04:52:35.1563123Z   Passed           : 34063 (98.47%)
2026-07-17T04:52:35.1563369Z   Expectedly Failed:    27 (0.08%)
2026-07-17T04:52:35.1563607Z   Unresolved       :     1 (0.00%)
2026-07-17T04:52:35.2002146Z FAILED: tools/lldb/test/CMakeFiles/check-lldb /home/gha/actions-runner/_work/llvm-project/llvm-project/build/tools/lldb/test/CMakeFiles/check-lldb 
```
which seems not related to the change.

https://github.com/llvm/llvm-project/pull/199808