[gimp] extensions, po-plug-ins: fix localization of extension metadata.

[Jehan <jehanp src gnome org>]

commit b9ad5d46ccae6e59681d5133951afbd34f68ab2a
Author: Jehan <jehan girinstud io>
Date:   Sat Oct 10 14:04:59 2020 +0200

    extensions, po-plug-ins: fix localization of extension metadata.
    
    The metadata format being appdata, I simply use standard intltool
    merging on the XML templates.
    For Automake, I use a custom rule instead of INTLTOOL_XML_RULE because
    the m4 macro hardcoded $(top_srcdir)/po as translation source directory
    (yet we want to use po-plug-ins/ for these). Meson on the other side
    already used a custom command.

 extensions/goat-exercises/Makefile.am | 5 ++++-
 extensions/goat-exercises/meson.build | 2 +-
 po-plug-ins/meson.build               | 1 +
 3 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/extensions/goat-exercises/Makefile.am b/extensions/goat-exercises/Makefile.am
index e9ff6beff6..1541d3c5dc 100644
--- a/extensions/goat-exercises/Makefile.am
+++ b/extensions/goat-exercises/Makefile.am
@@ -128,7 +128,10 @@ appstream_files = $(appstream_in_files:.xml.in=.xml)
 appdatadir = $(goat_exercise_c_libexecdir)
 appdata_DATA = $(appstream_files)
 
-@INTLTOOL_XML_RULE@
+org.gimp.extension.goat-exercises.metainfo.xml: org.gimp.extension.goat-exercises.metainfo.xml.in $(wildcard 
$(top_srcdir)/po-plug-ins/*.po)
+       $(INTLTOOL_MERGE) $(top_srcdir)/po-plug-ins $< $(@) -x -u -c 
$(top_builddir)/po-plug-ins/.intltool-merge-cache
+
+.PHONY: org.gimp.extension.goat-exercises.metainfo.xml
 
 EXTRA_DIST = \
        goat-exercise-gjs.js    \
diff --git a/extensions/goat-exercises/meson.build b/extensions/goat-exercises/meson.build
index d078690017..5169d56930 100644
--- a/extensions/goat-exercises/meson.build
+++ b/extensions/goat-exercises/meson.build
@@ -110,7 +110,7 @@ appdatafile = custom_target(appdatafilename,
   output: [ appdatafilename, ],
   command: [
     intltool_merge,
-    po_dir,
+    po_plug_ins_dir,
     '@INPUT@',
     '@OUTPUT@',
     '--xml-style',
diff --git a/po-plug-ins/meson.build b/po-plug-ins/meson.build
index 30c6f6f987..2f8bc85d28 100644
--- a/po-plug-ins/meson.build
+++ b/po-plug-ins/meson.build
@@ -1 +1,2 @@
+po_plug_ins_dir = meson.current_source_dir()
 i18n.gettext(gettext_package + '-std-plug-ins', preset: 'glib')