[compiler-rt] Added missing BitmapFirst and BitmapLast in InstrProfilingPlatformOth… (PR #96539)

[Alan Phipps via llvm-commits]

evodius96 wrote:

This will ensure there are no compile errors.  
Technically MC/DC, which relies on these functions, is unsupported for these "PlatformOther" cases as it is very difficult to test. So any references to the start/end routines ought to return NULL.

https://github.com/llvm/llvm-project/pull/96539