Index: head/share/mk/src.sys.obj.mk
===================================================================
--- head/share/mk/src.sys.obj.mk	(revision 325303)
+++ head/share/mk/src.sys.obj.mk	(revision 325304)
@@ -1,111 +1,112 @@
 # $FreeBSD$
 #
 # Early setup of MAKEOBJDIR
 #
 # Default format is: /usr/obj/usr/src/[${TARGET}.${TARGET_ARCH}/]bin/sh
 #  MAKEOBJDIRPREFIX is	/usr/obj
 #  OBJROOT is		/usr/obj/usr/src/
 #  OBJTOP is		/usr/obj/usr/src/[${TARGET}.${TARGET_ARCH}/]
 #  MAKEOBJDIR is	/usr/obj/usr/src/[${TARGET}.${TARGET_ARCH}/]bin/sh
 #
 #  MAKEOBJDIRPREFIX will override the default pattern above and internally
 #  set MAKEOBJDIR.  If OBJROOT is set then MAKEOBJDIRPREFIX is rooted inside
 #  of there.
 #
 #  If MK_UNIFIED_OBJDIR is no then OBJROOT will always match OBJTOP.
 #
 #  If .MAKE.LEVEL == 0 then the TARGET.TARGET_ARCH is potentially added on.
 #  If .MAKE.LEVEL >  0 and MAKEOBJDIRPREFIX is set then it will not get
 #  TARGET.TARGET_ARCH added in as it assumes that MAKEOBJDIRPREFIX is
 #  nested in the existing OBJTOP with TARGET.TARGET_ARCH in it.
 #
 
 _default_makeobjdirprefix?=	/usr/obj
 _default_makeobjdir=	$${.CURDIR:S,^$${SRCTOP},$${OBJTOP},}
 
 .include <bsd.mkopt.mk>
 
 .if ${.MAKE.LEVEL} == 0 || empty(OBJROOT)
 .if ${MK_UNIFIED_OBJDIR} == "no"
 # Fall back to historical behavior.
 # We always want to set a default MAKEOBJDIRPREFIX...
 MAKEOBJDIRPREFIX?=	${_default_makeobjdirprefix}
 # but don't enforce TARGET.TARGET_ARCH unless we're at the top-level directory.
 .if ${.CURDIR} == ${SRCTOP} && \
     !(defined(TARGET) && defined(TARGET_ARCH) && \
     ${MACHINE} == ${TARGET} && ${MACHINE_ARCH} == ${TARGET_ARCH} && \
     !defined(CROSS_BUILD_TESTING))
 MAKEOBJDIRPREFIX:=	${MAKEOBJDIRPREFIX}${TARGET:D/${TARGET}.${TARGET_ARCH}}
 .endif
 .endif	# ${MK_UNIFIED_OBJDIR} == "no"
 
 .if !empty(MAKEOBJDIRPREFIX)
 # put things approximately where they want
 OBJROOT:=	${MAKEOBJDIRPREFIX}${SRCTOP}/
 MAKEOBJDIRPREFIX=
-.export MAKEOBJDIRPREFIX
+# export but do not track
+.export-env MAKEOBJDIRPREFIX
 .endif
 .if empty(MAKEOBJDIR)
 # OBJTOP set below
 MAKEOBJDIR=	${_default_makeobjdir}
 # export but do not track
 .export-env MAKEOBJDIR
 # Expand for our own use
 MAKEOBJDIR:=	${MAKEOBJDIR}
 .endif
 # SB documented at http://www.crufty.net/sjg/docs/sb-tools.htm
 .if !empty(SB)
 SB_OBJROOT?=	${SB}/obj/
 # this is what we use below
 OBJROOT?=	${SB_OBJROOT}
 .endif
 OBJROOT?=	${_default_makeobjdirprefix}${SRCTOP}/
 .if ${OBJROOT:M*/} != ""
 OBJROOT:=	${OBJROOT:H:tA}/
 .else
 OBJROOT:=	${OBJROOT:H:tA}/${OBJROOT:T}
 .endif
 # Must export since OBJDIR will dynamically be based on it
 .export OBJROOT SRCTOP
 .endif
 
 .if ${MK_UNIFIED_OBJDIR} == "yes"
 OBJTOP:=	${OBJROOT}${TARGET:D${TARGET}.${TARGET_ARCH}:U${MACHINE}.${MACHINE_ARCH}}
 .else
 # TARGET.TARGET_ARCH handled in OBJROOT already.
 OBJTOP:=	${OBJROOT:H}
 .endif	# ${MK_UNIFIED_OBJDIR} == "yes"
 
 # Wait to validate MAKEOBJDIR until OBJTOP is set.
 .if defined(MAKEOBJDIR)
 .if ${MAKEOBJDIR:M/*} == ""
 .error Cannot use MAKEOBJDIR=${MAKEOBJDIR}${.newline}Unset MAKEOBJDIR to get default:  MAKEOBJDIR='${_default_makeobjdir}'
 .endif
 .endif
 
 # Fixup OBJROOT/OBJTOP if using MAKEOBJDIRPREFIX but leave it alone
 # for DIRDEPS_BUILD which really wants to know the absolute top at
 # all times.  This intenionally comes after adding TARGET.TARGET_ARCH
 # so that is truncated away for nested objdirs.  This logic also
 # will not trigger if the OBJROOT block above unsets MAKEOBJDIRPREFIX.
 .if !empty(MAKEOBJDIRPREFIX) && ${MK_DIRDEPS_BUILD} == "no"
 OBJTOP:=	${MAKEOBJDIRPREFIX}${SRCTOP}
 OBJROOT:=	${OBJTOP}/
 .endif
 
 # Assign this directory as .OBJDIR if possible
 .if ${MK_AUTO_OBJ} == "no"
 # The expected OBJDIR already exists, set it as .OBJDIR.
 .if !empty(MAKEOBJDIRPREFIX) && exists(${MAKEOBJDIRPREFIX}${.CURDIR})
 .OBJDIR: ${MAKEOBJDIRPREFIX}${.CURDIR}
 .elif exists(${MAKEOBJDIR})
 .OBJDIR: ${MAKEOBJDIR}
 # Special case to work around bmake bug.  If the top-level .OBJDIR does not yet
 # exist and MAKEOBJDIR is passed into environment and yield a blank value,
 # bmake will incorrectly set .OBJDIR=${SRCTOP}/ rather than the expected
 # ${SRCTOP} to match ${.CURDIR}.
 .elif ${MAKE_VERSION} <= 20170720 && \
     ${.CURDIR} == ${SRCTOP} && ${.OBJDIR} == ${SRCTOP}/
 .OBJDIR: ${.CURDIR}
 .endif
 .endif	# ${MK_AUTO_OBJ} == "no"