maint: Use xgettext.scm wrapper to create .PO files reproducibly.

* build-aux/xgettext.scm: New script.
* po/guix/Makevars (XGETTEXT): Set it.
(XGETTEXT_OPTIONS): Add --xgettext option to `real' xgettext.
* po/packages/Makevars (XGETTEXT): Set it.
(XGETTEXT_OPTIONS): Add --xgettext option to `real' xgettext.

Change-Id: I71b6b843970090f765f46ac346b92a346560e3f0

po/guix/Makevars

@@ -5,6 +5,10 @@ DOMAIN = guix
 subdir = po/guix
 top_builddir = ../..
 
+# We use our xgettext.scm wrapper to produce .PO files reproducibly using a
+# timestamp from Git.
+XGETTEXT:=$(top_srcdir)/build-aux/xgettext.scm
+
 # These options get passed to xgettext.  We want to catch standard
 # gettext uses, and SRFI-35 error condition messages.  In C++ code
 # we use 'n_' instead of the more usual 'N_' for no-ops.
@@ -14,7 +18,8 @@ XGETTEXT_OPTIONS =				\
   --keyword=message				\
   --keyword=description				\
   --keyword=synopsis				\
-  --keyword=n_
+  --keyword=n_					\
+  --xgettext=$(XGETTEXT_)
 
 COPYRIGHT_HOLDER = the authors of Guix (msgids)
 

po/packages/Makevars

@@ -6,12 +6,18 @@ DOMAIN = guix-packages
 subdir = po/packages
 top_builddir = ../..
 
+# We use our xgettext.scm wrapper to produce .PO files reproducibly using a
+# timestamp from Git.  The `real' xgettext is passed as an option to
+# xgettext.scm
+XGETTEXT:=$(top_srcdir)/build-aux/xgettext.scm
+
 # These options get passed to xgettext.  We want to catch exclusively package
 # synopses and descriptions.
 XGETTEXT_OPTIONS =				\
   --language=Scheme --from-code=UTF-8		\
-  --keyword=synopsis --keyword=description      \
-  --keyword=output-synopsis:2
+  --keyword=synopsis --keyword=description	\
+  --keyword=output-synopsis:2			\
+  --xgettext=$(XGETTEXT_)
 
 COPYRIGHT_HOLDER = the authors of Guix (msgids)