patch 8.2.4380: small differences between Chinese translation files

Problem:    Small differences between Chinese translation files.
Solution:   Add rule for converting UTF-8 to gb2312. (closes #9773)
diff --git a/src/po/Makefile b/src/po/Makefile
index e46bcea..47064fd 100644
--- a/src/po/Makefile
+++ b/src/po/Makefile
@@ -132,6 +132,12 @@
 	iconv -f iso-8859-2 -t cp1250 sk.po | \
 		sed -e 's/charset=ISO-8859-2/charset=cp1250/' -e 's/# Original translations/# Generated from sk.po, DO NOT EDIT/' > sk.cp1250.po
 
+# Convert zh_CN.UTF-8.po to create zh_CN.po.
+zh_CN.po: zh_CN.UTF-8.po
+	rm -f zh_CN.po
+	iconv -f UTF-8 -t gb2312 zh_CN.UTF-8.po | \
+		sed -e 's/charset=[uU][tT][fF]-8/charset=gb2312/' -e 's/# Original translations/# Generated from zh_CN.UTF-8.po, DO NOT EDIT/' > zh_CN.po
+
 # Convert zh_CN.UTF-8.po to create zh_CN.cp936.po.
 # Set 'charset' to gbk to avoid that msfmt generates a warning.
 # This used to convert from zh_CN.po, but that results in a conversion error.