The macros utilise bazel "transitions" to set the `make` toolchain used
in the configure_make(), cmake() or make() rules to
a given make variant toolchain, e.g. preinstalled_nmake.
Note that the msvc constraint was removed from the
`exec_compatible_with` attribute of `preinstalled_nmake_toolchain` as
the condition is not actually met even when building with msvc. See
https://github.com/bazelbuild/bazel/issues/7730.
This will be tested in PR#729