[llvm] CMake: Fix LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING in reentrancy situa… (PR #144331)

[NAKAMURA Takumi via llvm-commits]

https://github.com/chapuni commented:

Why do you proceed this w/o mentioning original author(s)? @SLTozer #107278 #143590

I guess it would just work but nasty. This should be rewritten w/o modifying cache vars, finally.

I also guess this would be tolerant of `cmake -DLLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING=0`. Is it intented?

If you want it to be a workaround, you may reduce affected lines, e.g.
```
string(TOUPPER "${LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING}" uppercase_LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING)

if( uppercase_LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING STREQUAL "0" OR uppercase_LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING STREQUAL "1")
  # Do nothing.
elseif( uppercase_LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING STREQUAL "COVERAGE" )
```

https://github.com/llvm/llvm-project/pull/144331