Explicitly enable .MAKE.ALWAYS_PASS_JOB_QUEUE for bmake.

This is a NOP as r254419 enabled this by default in bmake.  Add it here though
to ensure it is known that we are using this as a default and in case a
bmake import removes the default we have.

This tells bmake to always pass job tokens into sub-commands.  Otherwise
it would only do so if the target being built depended on the special
.MAKE target (which causes _all_ commands to be executed with -n as well)
or if the command matches '${MAKE}/${.MAKE}/$(MAKE)/$(.MAKE)/make' (before
expansion, so ${LIB32WMAKE} would not qualify).  Using '+' on a command
(which runs the command with -n) would not pass the job token even though it
is a documented way to achieve the .MAKE effect on a command.

Sponsored by:	EMC / Isilon Storage Division

share/mk/sys.mk

@@ -394,6 +394,10 @@ SHELL=	${__MAKE_SHELL}
 # Tell bmake the makefile preference
 .MAKE.MAKEFILE_PREFERENCE= BSDmakefile makefile Makefile
 
+# Tell bmake to always pass job tokens, regardless of target depending on
+# .MAKE or looking like ${MAKE}/${.MAKE}/$(MAKE)/$(.MAKE)/make.
+.MAKE.ALWAYS_PASS_JOB_QUEUE= yes
+
 # By default bmake does *not* use set -e
 # when running target scripts, this is a problem for many makefiles here.
 # So define a shell that will do what FreeBSD expects.