[gtksourceview] build: use proper dylib versioning on macOS

[Christian Hergert <chergert src gnome org>]

commit a70ac3a61776bfd7a95166377b68f8784e6dec85
Author: Tom Schoonjans <Tom Schoonjans diamond ac uk>
Date:   Tue Sep 10 10:28:26 2019 +0100

    build: use proper dylib versioning on macOS

 gtksourceview/meson.build |  1 +
 meson.build               | 12 ++++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)
---
diff --git a/gtksourceview/meson.build b/gtksourceview/meson.build
index 14603ffe..82a28d2b 100644
--- a/gtksourceview/meson.build
+++ b/gtksourceview/meson.build
@@ -248,6 +248,7 @@ if cc.get_id() == 'msvc'
 else
   gtksource_lib = shared_library(package_string, gtksource_res,
                   version: lib_version,
+          darwin_versions: lib_osx_version,
       include_directories: gtksourceview_include_dirs,
              dependencies: gtksource_deps,
                link_whole: gtksource_libs,
diff --git a/meson.build b/meson.build
index 78c2fc59..5936d177 100644
--- a/meson.build
+++ b/meson.build
@@ -21,10 +21,14 @@ version_micro = version_arr[2].to_int()
 api_version = '4'
 
 lib_version = '0.0.0'
-lib_version_arr = version.split('.')
-lib_version_major = version_arr[0].to_int()
-lib_version_minor = version_arr[1].to_int()
-lib_version_micro = version_arr[2].to_int()
+lib_version_arr = lib_version.split('.')
+lib_version_major = lib_version_arr[0].to_int()
+lib_version_minor = lib_version_arr[1].to_int()
+lib_version_micro = lib_version_arr[2].to_int()
+
+osx_current = lib_version_major + 1
+lib_osx_version = [osx_current, '@0@.@1@'.format(osx_current, lib_version_minor)]
+
 
 package_name = meson.project_name()
 package_string = '@0@-@1@'.format(package_name, api_version)