cmGlobalGenerator: FindMakeProgram() at a generator-specific time

d5b5c192 moved FindMakeProgram() to an earlier time, which resulted
in CMAKE_MAKE_PROGRAM not being read from the toolchain file. Change
it to only call FindMakeProgram() early in the specific cases of
Visual Studio and Xcode, and restore the old behavior for all other
generators.

Fixes: #21486
4 files changed