Dump temacs in an empty environment to prevent -dev paths from ending
up in the dumped image.

diff --git a/src/Makefile.in b/src/Makefile.in
index fd05a45df5..13f529c253 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -570,7 +570,7 @@ emacs$(EXEEXT): temacs$(EXEEXT) \
                 lisp.mk $(etc)/DOC $(lisp) \
                 $(lispsource)/international/charprop.el ${charsets}
 ifeq ($(DUMPING),unexec)
-	LC_ALL=C $(RUN_TEMACS) -batch $(BUILD_DETAILS) -l loadup --temacs=dump
+	env -i LC_ALL=C $(RUN_TEMACS) -batch $(BUILD_DETAILS) -l loadup --temacs=dump
   ifneq ($(PAXCTL_dumped),)
 	      $(PAXCTL_dumped) emacs$(EXEEXT)
   endif