Bug 1656141 - Remove EMBED_MANIFEST_AT. r=froydnj

It was only ever set to the same value as its default, except in
comm-central, where it is unset, but in directories that now don't link
anything (they did back when binary components were a thing).

Differential Revision: https://phabricator.services.mozilla.com/D85381

accessible/interfaces/ia2/Makefile.in

@@ -65,8 +65,6 @@ MIDL_UNUSED_GENERATED_FILES = \
   $(MIDL_LIBRARIES:%.idl=%.c) \
   $(NULL)
 
-EMBED_MANIFEST_AT = 2
-
 INSTALL_TARGETS += midl
 midl_FILES := $(filter %.h %_i.c,$(MIDL_GENERATED_FILES))
 midl_DEST = $(DIST)/include

accessible/interfaces/msaa/Makefile.in

@@ -29,8 +29,6 @@ export:: done_gen
 register::
 	regsvr32 -s $(DIST)/bin/$(SHARED_LIBRARY)
 
-EMBED_MANIFEST_AT = 2
-
 midl_exports := \
     ISimpleDOM.h \
     ISimpleDOM_i.c \

config/rules.mk

@@ -103,8 +103,6 @@ ifdef LIB_IS_C_ONLY
 MKSHLIB			= $(MKCSHLIB)
 endif
 
-EMBED_MANIFEST_AT=2
-
 endif # MKSHLIB
 endif # FORCE_SHARED_LIB
 
@@ -610,15 +608,13 @@ endif
 
 ifeq (_WINNT,$(GNU_CC)_$(OS_ARCH))
 ifdef MSMANIFEST_TOOL
-ifdef EMBED_MANIFEST_AT
 	@if test -f $@.manifest; then \
 		echo "Manifest in objdir is not supported"; \
 		exit 1; \
 	elif test -f '$(srcdir)/$@.manifest'; then \
 		echo 'Embedding manifest from $(srcdir_rel)/$@.manifest'; \
-		$(call WINEWRAP,$(MT)) -NOLOGO -MANIFEST '$(srcdir_rel)/$@.manifest' -OUTPUTRESOURCE:$@\;$(EMBED_MANIFEST_AT); \
+		$(call WINEWRAP,$(MT)) -NOLOGO -MANIFEST '$(srcdir_rel)/$@.manifest' -OUTPUTRESOURCE:$@\;2; \
 	fi
-endif   # EMBED_MANIFEST_AT
 endif	# MSVC with manifest tool
 endif	# WINNT && !GCC
 	chmod +x $@