The lack of this causes my TLS-ized source tree to fail to build when I enable modules, because the necessary -I flags are not being passed to the compiler. This seems like a good idea, anyway, as modules may very well depend on nonstandard include paths that were passed to configure.
diff -r 2dee57a2c2d6 modules/ChangeLog
--- a/modules/ChangeLog Wed Aug 06 10:19:25 2014 +0100
+++ b/modules/ChangeLog Mon Aug 11 15:04:24 2014 -0600
@@ -1,3 +1,7 @@
+
+ * common/Makefile.common (CPPFLAGS): New variable.
+
* XEmacs 21.5.34 "kale" is released.
diff -r 2dee57a2c2d6 modules/common/Makefile.common
--- a/modules/common/Makefile.common Wed Aug 06 10:19:25 2014 +0100
+++ b/modules/common/Makefile.common Mon Aug 11 15:01:27 2014 -0600
@@ -35,6 +35,7 @@
RM=rm -f
PROGNAME=@PROGNAME@
CFLAGS=@XE_CFLAGS@
+CPPFLAGS=@CPPFLAGS@
INSTALL=@INSTALL@
version=@version@
prefix=@prefix@
@@ -67,7 +68,7 @@
all: $(OBJECT_TO_BUILD)
.c.o:
- $(MODCC) $(MODCFLAGS) -c $<
+ $(MODCC) $(MODCFLAGS) $(CPPFLAGS) -c $<
$(MODNAME).ell: $(OBJS) $(MODNAME)_i.o $(IMPORT_LIB)
$(MODCC) --mode=link --mode=verbose --mod-output=$@ \