My experience is the exact opposite. Moving a multimillion line C++ code base from msbuild to CMake/ninja on Windows cut the build time in half.
Chrome got even better speedups I believe by building with clang/ninja on Windows.
Bazel is where the real benefits lie by reusing other people's (or CI machine's) partial build artifacts via a centralized cache and by avoiding to run tests that are not affected by code changes.
Seems it has the necessary integration points to run CMake builds as an external command. The same way you could build Make, Autotools, Meson or Bazel projects from CMake with the necessary external command plumbings.
Obviously both fille the same purpose of being a build system, though Bazel is also a build executor not just a generator. Integration would mean either adding BUILD language support to CMake or vice-versa, but you wouldn't get the particular benefits of either this way.
Chrome got even better speedups I believe by building with clang/ninja on Windows.
Bazel is where the real benefits lie by reusing other people's (or CI machine's) partial build artifacts via a centralized cache and by avoiding to run tests that are not affected by code changes.