[macdoc] Fix logging line in Makefile.

That line was working fine before because the Makefile was incorrectly using the system X.S to build, but since we reverted back to use the just compiled X.S the command line changed to include a '&&' token.

Since the echo command doesn't correctly escape the variable expansion, the second command (mdtool build) is ran and later on destroyed by the rm -rf, that is not sufficient though to trigger the next (and correct) mdtool build from properly recreating the .app