po/Makefile: Modern shell scripting (use $() instead of ``)

Various shell files contain a mix between obsolete ``
and modern $(); It would be nice to convert to using $()
everywhere.

Signed-off-by: Mao Zhongyi <maozhongyi@cmss.chinamobile.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

po/Makefile

@@ -36,7 +36,7 @@ clean:
 
 install: $(OBJS)
 	for obj in $(OBJS); do \
-	    base=`basename $$obj .mo`; \
+	    base=$$(basename $$obj .mo); \
 	    $(INSTALL) -d $(DESTDIR)$(prefix)/share/locale/$$base/LC_MESSAGES; \
 	    $(INSTALL) -m644 $$obj $(DESTDIR)$(prefix)/share/locale/$$base/LC_MESSAGES/qemu.mo; \
 	done