Get CMake bin dir from CMake module if possible

[timmoon10]

Description

The build system attempts to get the CMake executable from the cmake module. However, there is a subtle edge case when the user does not have the module installed but does have a directory called cmake in their path. In this case, Python loads the wrong thing during import cmake and our detection logic throws an error (https://github.com/NVIDIA/TransformerEngine/issues/887). This PR fixes this issue by attempting to load the CMAKE_BIN_DIR variable from cmake, which will only succeed if the correct cmake is imported.

Type of change

• [ ] Documentation change (change only to the documentation, either a fix or a new content)
• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Changes

• Get CMake bin dir from CMake module if possible

Checklist:

• [x] I have read and followed the contributing guidelines
• [x] The functionality is complete
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes

[timmoon10]

/te-ci

[ksivaman]

Closing in favor of #877