Don't assume that make(1) is a bsd-like make program. It might not be. This

only matters in the early stages of bootstrapping, of course, but gnu make can't
handle bsd make Makefiles at all if they use any of the 'dot' directives, which
src/Makefile has in abudnance.

Makefile

@@ -234,17 +234,19 @@ upgrade_checks:
 	    PATH=${PATH} ${BINMAKE} obj >/dev/null 2>&1 && \
 	    PATH=${PATH} ${BINMAKE} >/dev/null 2>&1); \
 	then \
-	    (cd ${.CURDIR} && make make); \
+	    (cd ${.CURDIR} && ${BSDMAKE} make); \
 	fi
 
 #
 # Upgrade make(1) to the current version using the installed
-# headers, libraries and tools.
+# headers, libraries and tools.  Also, allow the location of
+# the system bsdmake-like utility to be overridden.
 #
+BSDMAKE?=make
 MMAKEENV=	MAKEOBJDIRPREFIX=${MAKEPATH} \
 		DESTDIR= \
 		INSTALL="sh ${.CURDIR}/tools/install.sh"
-MMAKE=		${MMAKEENV} make \
+MMAKE=		${MMAKEENV} ${BSDMAKE} \
 		-D_UPGRADING \
 		-DNOMAN -DNO_MAN -DNOSHARED -DNO_SHARED \
 		-DNO_CPU_CFLAGS -DNO_WERROR