[gimp] build: (meson) fix building with -Dwindows-installer=true option.

[Jehan <jehanp src gnome org>]

commit cb6a1a75c9348f984ca3d178ee0fba9d124cfe55
Author: Jehan <jehan girinstud io>
Date:   Sat Aug 22 19:02:14 2020 +0200

    build: (meson) fix building with -Dwindows-installer=true option.
    
    Fixes:
    > build/windows/installer/lang/meson.build:49:2: ERROR: Unknown variable "code".

 build/windows/installer/lang/meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/build/windows/installer/lang/meson.build b/build/windows/installer/lang/meson.build
index c86aeabf66..afbd1e05d6 100644
--- a/build/windows/installer/lang/meson.build
+++ b/build/windows/installer/lang/meson.build
@@ -46,7 +46,7 @@ extractlang = find_program('extractlang.sh')
 all_isl = []
 foreach language : languages
   lang_code    = language.get('code')
-  lang_prefix  = language.get('prefix', '[@0@]'.format(code))
+  lang_prefix  = language.get('prefix', '[@0@]'.format(lang_code))
   lang_encoding= language.get('encoding', 'WINDOWS-1252')
 
   islfile = '@0  setup isl'.format(lang_code)