[dia] build: Fix doc building

[Jan Tojnar <jtojnar src gnome org>]

commit 9e6a625c5eb75e732a401c7613ade189c8b07682
Author: Jan Tojnar <jtojnar gmail com>
Date:   Tue Apr 7 08:04:29 2020 +0200

    build: Fix doc building
    
    The installations were failing because doc/de/apa.html could not be found.
    It was actually generated in doc/ directory.
    
    As per xsltproc(1), the directories passed to `--output` flag need to end with /:
    
    > This means, that e.g. -o directory will maybe not work, but -o directory/ will.
    
    Otherwise, the program will consider the path a file and generate the outputs
    relative to its parent.

 doc/de/meson.build | 2 +-
 doc/en/meson.build | 2 +-
 doc/eu/meson.build | 2 +-
 doc/fr/meson.build | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/doc/de/meson.build b/doc/de/meson.build
index 69a8884b..9115c60a 100644
--- a/doc/de/meson.build
+++ b/doc/de/meson.build
@@ -69,7 +69,7 @@ if xsltproc.found()
         command: [
             xsltproc,
             '--stringparam', 'graphic.default.extension', 'png',
-            '-o', '@OUTDIR@',
+            '--output', '@OUTDIR@/',
             '@INPUT@'
         ],
         depend_files: xml_deps,
diff --git a/doc/en/meson.build b/doc/en/meson.build
index aad39cfd..4217e22a 100644
--- a/doc/en/meson.build
+++ b/doc/en/meson.build
@@ -102,7 +102,7 @@ if xsltproc.found()
         command: [
             xsltproc,
             '--stringparam', 'graphic.default.extension', 'png',
-            '-o', '@OUTDIR@',
+            '--output', '@OUTDIR@/',
             '@INPUT@'
         ],
         depend_files: xml_deps,
diff --git a/doc/eu/meson.build b/doc/eu/meson.build
index de00c015..9a5b9c25 100644
--- a/doc/eu/meson.build
+++ b/doc/eu/meson.build
@@ -61,7 +61,7 @@ if xsltproc.found()
         command: [
             xsltproc,
             '--stringparam', 'graphic.default.extension', 'png',
-            '-o', '@OUTDIR@',
+            '--output', '@OUTDIR@/',
             '@INPUT@'
         ],
         depend_files: xml_deps,
diff --git a/doc/fr/meson.build b/doc/fr/meson.build
index c6cce846..cc97bb05 100644
--- a/doc/fr/meson.build
+++ b/doc/fr/meson.build
@@ -72,7 +72,7 @@ if xsltproc.found()
         command: [
             xsltproc,
             '--stringparam', 'graphic.default.extension', 'png',
-            '-o', '@OUTDIR@',
+            '--output', '@OUTDIR@/',
             '@INPUT@'
         ],
         depend_files: xml_deps,