Only works with some versions and seems to break with cygwin. I'm
working on using a recent upstream version + patches.
This reverts commit 848f165ceb54b0c7ae3e52ad7ad50c258db2956c.
...and whoever had the bad idea to make the downloaded GLM_TARBALL
bae83fa5dc7f081768daace6e199adc3-glm-0.9.4.6-libreoffice.zip to already be
patched with that broken patch (external/glm/Wshadow-unix.patch or
external/glm/Wshadow-windows.patch or whatever?) instead of applying locally via
gb_UnpackedTarball_add_patches...
Change-Id: I0053346f626cc3af42f7ea82a7a26c8b47876a98