[clang] [clang-scan-deps] Infer the tool locations from PATH (PR #108539)

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

Can you explain why exactly is this necessary/beneficial? If the compilation database got created with just the tool name, I'd expect the rest of the build to be able to use just the tool name when the scanner spits it out again, no? If this is about the scanner finding the right config, sysroot, resource directory, etc., I'd expect that to already happen, since the scanner needs to be colocated with the toolchain itself (since `clang` and `clang-scan-deps` are effectively version-locked).

https://github.com/llvm/llvm-project/pull/108539