Makefile: Use basename in a POSIX-compliant way.

If you aren't using GNU coreutils, chances are that your basename
doesn't know about the -s argument. Luckily for us, basename does what
we need it do even without the -s argument.

Change-Id: I8b81a429bb037b997ee6640ff8a2b5e860962bb7

Makefile

@@ -493,7 +493,7 @@ doc/core-en_US.xml: makeopts .lastclean $(XML_core_en_US)
 			MODULEINFO=$$($(AWK) -f build_tools/get_moduleinfo $$i) ; \
 			if [ -n "$$MODULEINFO" ] ; \
 			then \
-				echo "<module language=\"en_US\" name=\"`$(BASENAME) -s .c $$i`\">" >> $@ ; \
+				echo "<module language=\"en_US\" name=\"`$(BASENAME) $$i .c`\">" >> $@ ; \
 				echo "$$MODULEINFO" >> $@ ; \
 				echo "</module>" >> $@ ; \
 			fi ; \