[CMake] Disable `builtin_glew` on macOS

[guitargeek]

The CMake issue that made is necessary to use builtin_glew was apparently fixed last year: https://gitlab.kitware.com/cmake/cmake/-/commit/a31b27078595fce911b2469937ac12934555644a

I checked that the CMake versions on all the three macOS platforms include the fix.

The workaround that this commit reverts was introduced here: https://github.com/root-project/root/pull/5458

[github-actions[bot]]

Test Results

     8 files       8 suites   2d 1h 23m 31s :stopwatch:  2 597 tests  2 597 :white_check_mark: 0 :zzz: 0 :x: 19 841 runs  19 841 :white_check_mark: 0 :zzz: 0 :x:

Results for commit 4528efcd.

:recycle: This comment has been updated with latest results.

[guitargeek]

Interesting for learning what would happen.