Merge pull request #1147 from RosettaCommons/roccomoretti/cmake_linker
Make CMake builds slightly faster
This cherry picks two efficiency improvements from pull request #958
1. Convert from using the python script smart_symlink.py to using the CMake-internal symlinking facility.
2. Adjust version.py not to re-write the version header if it hasn't changed.
On my machine, these improvements speed up a no-change rebuild by about a factor of 3 or so. (Symlinking now takes less than a second.) The speedups also (slightly) help with normal rebuilds.