Instead of creating a single solver/*/installation/program -> ../../bin symlink
used by all gb_CppunitTest_use_executable together, individually copy each
gb_CppunitTest_use_executable into a true solver/*/install/program/ diretory.
(Renamed solver/*/installation/ to solver/*/install/ so that old existing
solver/*/installation/program symlinks on non-Windows platforms would not
interfere with the new cp rule.)

Change-Id: I4ce82b41856056669ad074ff2ef8004fdc6533c1