fix make distcheck

Makefile.am

@@ -79,15 +79,17 @@ README.gz: $(top_srcdir)/README
 	-gzip -9 < $< > $@
 
 THANKS.gz: $(top_srcdir)/THANKS
-	sed -e 's/^#.*//' $< > $<.tmp # strip comments
-	sed -e '/^$$/d' $<.tmp > $<.tmp2  # strip empty lines
+	TMP1=`mktemp -t THANKS`
+	TMP2=`mktemp -t THANKS`
+	sed -e 's/^#.*//' $< > $TMP1 # strip comments
+	sed -e '/^$$/d' $TMP1 > $TMP2  # strip empty lines
 	git shortlog -se 6c976bd..HEAD \
 	 | grep -v @apache.org \
 	 | sed -E 's/^[[:blank:]]{5}[[:digit:]]+[[:blank:]]/ * /' \
-	 >> $<.tmp2 # inject git authors
-	echo '\nFor a list of authors see the `AUTHORS` file.\n' >> $<.tmp2
-	-gzip -9 < $<.tmp2 > $@ # zip
-	rm $<.tmp $<.tmp2 # cleanup
+	 >> $TMP2 # inject git authors
+	echo '\nFor a list of authors see the `AUTHORS` file.\n' >> $TMP2
+	-gzip -9 < $TMP2 > $@ # zip
+	rm $TMP1 $TMP2 # cleanup
 
 check: dev check-js
 	$(top_builddir)/test/etap/run $(top_srcdir)/test/etap