Use the '+' flag to make make recurse into sub-directories even when

given -n. For POLA reasons this behaviour is switched on only when
at least two -n flags are given to make. One -n flag keeps the old behaviour
of showing the shell command that would recurse into the sub-directories.

Discussed with: ru

share/mk/bsd.subdir.mk

@@ -35,14 +35,14 @@ DISTRIBUTION?=	base
 .if !target(distribute)
 distribute:
 .for dist in ${DISTRIBUTION}
-	cd ${.CURDIR}; \
+	${_+_}cd ${.CURDIR}; \
 	    ${MAKE} install -DNO_SUBDIR DESTDIR=${DISTDIR}/${dist} SHARED=copies
 .endfor
 .endif
 
 _SUBDIR: .USE
 .if defined(SUBDIR) && !empty(SUBDIR) && !defined(NO_SUBDIR)
-	@for entry in ${SUBDIR}; do \
+	@${_+_}for entry in ${SUBDIR}; do \
 		if test -d ${.CURDIR}/$${entry}.${MACHINE_ARCH}; then \
 			${ECHODIR} "===> ${DIRPRFX}$${entry}.${MACHINE_ARCH}"; \
 			edir=$${entry}.${MACHINE_ARCH}; \
@@ -58,12 +58,12 @@ _SUBDIR: .USE
 .endif
 
 ${SUBDIR}::
-	@if test -d ${.TARGET}.${MACHINE_ARCH}; then \
+	${_+_}@if test -d ${.TARGET}.${MACHINE_ARCH}; then \
 		cd ${.CURDIR}/${.TARGET}.${MACHINE_ARCH}; \
 	else \
 		cd ${.CURDIR}/${.TARGET}; \
 	fi; \
-	${MAKE} all
+	${_+_}${MAKE} all
 
 
 .for __target in all all-man checkdpadd clean cleandepend cleandir \
@@ -80,7 +80,7 @@ ${__stage}${__target}: _SUBDIR
 .endif
 .endfor
 ${__target}:
-	cd ${.CURDIR}; ${MAKE} build${__target}; ${MAKE} install${__target}
+	${_+_}cd ${.CURDIR}; ${MAKE} build${__target}; ${MAKE} install${__target}
 .endfor
 
 .if !target(install)

share/mk/sys.mk

@@ -57,6 +57,12 @@ ECHODIR		?=	true
 .endif
 .endif
 
+.if !empty(.MAKEFLAGS:M-n) && ${.MAKEFLAGS:M-n} == "-n"
+_+_		?=
+.else
+_+_		?=	+
+.endif
+
 .if defined(%POSIX)
 FC		?=	fort77
 FFLAGS		?=	-O 1