bootstrap: use shell rather than find and sed

bootstrap

@@ -61,9 +61,9 @@ fi
 ###
 
 echo "generating modules/**/Makefile.am"
-find modules/ -name Modules.am | \
-sed -ne 's,modules/\(.*\)/Modules.am,\1,p' | \
-while read d; do
+for d in modules/*/Modules.am modules/gui/*/Modules.am; do
+	d="${d#modules/}"
+	d="${d%/Modules.am}"
 	${CONFIG_SHELL-sh} modules/genmf "$d"
 	printf "."
 done