Internal libga: lib64/ vs. lib/

When installing with -DGA=ON and -DGA_BUILD=ON, the build system first makes the file libga.a in External/GlobalArrays_install/lib64/ (while compiling Global Arrays), and later looks for it in External/GlobalArrays_install/lib/ (while compiling alaska.exe).

See thread https://molcasforum.univie.ac.at/viewtopic.php?id=879