cmNinjaTargetGenerator: Remove unnecessary mkdirs
This avoids many duplicated MakeDirectory
calls, which result in potentially expensive syscalls.
Benchmarks on Windows show an improvement of ~100ms when configuring CMake itself:
Before:
Time (mean ± σ): 16.457 s ± 0.051 s [User: 0.000 s, System: 0.003 s]
Range (min … max): 16.406 s … 16.553 s 10 runs
After:
Time (mean ± σ): 16.369 s ± 0.032 s [User: 0.000 s, System: 0.006 s]
Range (min … max): 16.324 s … 16.441 s 10 runs