build: pass down AM_CFLAGS to sub-makes

Honor ipset/Makefile.am's AM_CFLAGS when compiling extensions.

Makefile.extra

@@ -1,6 +1,7 @@
 # -*- Makefile -*-
 # AUTOMAKE
 
+export AM_CFLAGS
 XA_SRCDIR = ${srcdir}
 XA_TOPSRCDIR = ${top_srcdir}
 XA_ABSTOPSRCDIR = ${abs_top_srcdir}

Makefile.iptrules.in

@@ -13,10 +13,8 @@ CCLD            = ${CC}
 CFLAGS          = @CFLAGS@
 LDFLAGS         = @LDFLAGS@
 
-regular_CFLAGS  = @regular_CFLAGS@
 libxtables_CFLAGS = @libxtables_CFLAGS@
 libxtables_LIBS   = @libxtables_LIBS@
-AM_CFLAGS         = ${regular_CFLAGS} ${libxtables_CFLAGS} -I${abs_top_srcdir}/extensions
 AM_DEPFLAGS     = -Wp,-MMD,$(@D)/.$(@F).d,-MT,$@
 
 AM_DEFAULT_VERBOSITY = 0

extensions/Makefile.am

@@ -1,6 +1,8 @@
 # -*- Makefile -*-
 # AUTOMAKE
 
+AM_CFLAGS = ${regular_CFLAGS} ${libxtables_CFLAGS} -I${abs_top_srcdir}/extensions
+
 # Not having Kbuild in Makefile.extra because it will already recurse
 .PHONY: modules modules_install clean_modules