Merge branch 'jc/install-no-hardlinks'

Your build platform may support hardlinks but you may prefer not to use them, e.g. when installing to DESTDIR to make a tarball and untarring on a filesystem that has poor support for hardlinks. The Makefile in git-gui project may need to learn to honor the same setting; it unconditionally creates git-citool by hardlinking git-gui. * jc/install-no-hardlinks: Makefile: NO_INSTALL_HARDLINKS