If 'make *clean*' is ran and the expected __objdir does not exist and cannot
be used as .OBJDIR then fallback to .CURDIR.

diff --git share/mk/auto.obj.mk share/mk/auto.obj.mk
index b633937674be..bb656d1c11dd 100644
--- share/mk/auto.obj.mk
+++ share/mk/auto.obj.mk
@@ -66,6 +66,8 @@ __objdir_made != echo ${__objdir}/; umask ${OBJDIR_UMASK:U002}; \
 .if !(${__objdir:M/*} == "" && ${.OBJDIR:tA} == ${${.CURDIR}/${__objdir}:L:tA})
 .error could not use ${__objdir}: .OBJDIR=${.OBJDIR}
 .endif
+.elif ${__objdir_made:Uno} == "no" && ${.OBJDIR:tA} != ${__objdir:tA}
+.OBJDIR: ${.CURDIR}
 .endif
 .endif
 .endif