Revert rev. 1.378, and restore the correct arithmetic expression

syntax.  The

	make buildworld
	mv /usr/include /usr/include.old
	make installworld

issue has been fixed a month ago in Makefile,v 1.285, and there
is no valid reason to continue to keep the wrong syntax here --
buildworld takes care of upgrading a make for you if necessary.
But if you find yourself in an environment with an old make(1)
binary that breaks on this, and this is because you attempted
to run a target other than buildworld, don't whine but try again
with -DALWAYS_CHECK_MAKE defined -- it should do the trick.
Otherwise, if you still have a problem, please report it as a
bug and attach the ``make -dl ...'' output.

Reviewed by:	marcel

Makefile.inc1

@@ -758,7 +758,7 @@ _btxld=		usr.sbin/btxld
 
 .if (!defined(NO_RESCUE) || \
     defined(RELEASEDIR)) && \
-    ( ${TARGET_ARCH} != ${MACHINE_ARCH} || ${BOOTSTRAPPING} < 501101 )
+    (${TARGET_ARCH} != ${MACHINE_ARCH} || ${BOOTSTRAPPING} < 501101)
 _crunchide=	usr.sbin/crunch/crunchide
 .endif