Auto-create bmake/unit-tests objdir if appropriate

Given the way bmake/unit-tests is visited, when doing 'test'
MK_AUTO_OBJ=yes will not be effective.
So create the objdir before running the sub-make.

Also ensure MAKEOBJDIR is passed to opt-m-include-dir

Reviewed by: deo

usr.bin/bmake/Makefile

@@ -147,11 +147,24 @@ ${OBJS}: config.h
 
 # A simple unit-test driver to help catch regressions
 TEST_MAKE ?= ${.OBJDIR}/${PROG:T}
-accept test:
+accept test: .NOMETA
 	cd ${.CURDIR}/unit-tests && \
 	MAKEFLAGS= ${TEST_MAKE} -r -m / ${.TARGET} ${TESTS:DTESTS=${TESTS:Q}}
 
 
+.if make(test) && ${MK_AUTO_OBJ} == "yes"
+# because of the way unit-tests is visted for test
+# the objdir will not be auto-created as expected.
+.if defined(MAKEOBJDIRPREFIX) || ${MAKEOBJDIR:Uno:M*/*} != ""
+_utobj = ${.OBJDIR}/unit-tests
+.else
+_utobj = ${.CURDIR}/unit-tests/${MAKEOBJDIR:Uobj}
+.endif
+utobj: .NOMETA
+	mkdir -p ${_utobj}
+test: utobj
+.endif
+
 # override some simple things
 BINDIR= /usr/bin
 MANDIR= /usr/share/man/man

usr.bin/bmake/unit-tests/Makefile

@@ -505,6 +505,7 @@ ENV.depsrc-optional+=   TZ=UTC
 ENV.deptgt-phony+=	MAKESYSPATH=.
 ENV.directive-undef=	ENV_VAR=env-value
 ENV.envfirst=		FROM_ENV=value-from-env
+ENV.opt-m-include-dir=	${MAKEOBJDIR:DMAKEOBJDIR=${MAKEOBJDIR}}
 ENV.varmisc=		FROM_ENV=env
 ENV.varmisc+=		FROM_ENV_BEFORE=env
 ENV.varmisc+=		FROM_ENV_AFTER=env