setting GIT_VERSION for cmake options has no effect on version in the binary

[stangri]

@aarond10 @baranyaib90 this issue has grown in importance since OpenWrt now mangles the PKG_RELEASE variable outside of the package's Makefile control for development branch, but not release branch.

I'm building the package not from git repo, but from the github archive and setting GIT_VERSION in the OpenWrt makefile, doesn't seem to affect anything so I ended up needing to create a patch which I update based on version from the Makefile with my own automation.

I wonder if it's some logic in the CMakeLists.txt that needs to be updated for the build process to pick up the value of GIT_VERSION when building from gzipped source rather than git checkout or if I'm doing something wrong, but if I could get rid of the patch and be able to set the version from the OpenWrt Makefile, it might make my life much easier maintaining the package for both development and release branches.