po/Makefile: fix $SRC_PATH reference

The rule for messages.po appears to be slightly wrong.
Move the `cd' command within parens.
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>
Tested-by: NStefan Weil <sw@weilnetz.de>

po/Makefile

@@ -37,8 +37,8 @@ install: $(OBJS)
 	$(call quiet-command, msgfmt -o $@ $<, "  GEN   $@")
 
 $(PO_PATH)/messages.po: $(SRC_PATH)/ui/gtk.c
-	$(call quiet-command, cd $(SRC_PATH) && \
-	 (xgettext -o - --from-code=UTF-8 --foreign-user \
+	$(call quiet-command, ( cd $(SRC_PATH) && \
+          xgettext -o - --from-code=UTF-8 --foreign-user \
 	    --package-name=QEMU --package-version=$(VERSION) \
 	    --msgid-bugs-address=qemu-devel@nongnu.org -k_ -C ui/gtk.c | \
 	  sed -e s/CHARSET/UTF-8/) >$@, "  GEN   $@")