[mm-common] skeletonmm, Meson build: Fix versioning on macOS

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 15a7349b3491a022975dc9284bada28de2b2530b
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Tue Sep 29 15:13:59 2020 +0200

    skeletonmm, Meson build: Fix versioning on macOS
    
    See https://github.com/libsigcplusplus/libsigcplusplus/pull/65

 skeletonmm/meson.build                     | 7 ++++++-
 skeletonmm/skeleton/skeletonmm/meson.build | 4 +++-
 2 files changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/skeletonmm/meson.build b/skeletonmm/meson.build
index 717c49e..b3b2baa 100644
--- a/skeletonmm/meson.build
+++ b/skeletonmm/meson.build
@@ -29,7 +29,12 @@ libtool_soversion = [0, 0, 0]
 skeletonmm_libversion = '@0@.@1@.@2@'.format(
   libtool_soversion[0] - libtool_soversion[2],
   libtool_soversion[2],
-  libtool_soversion[1])
+  libtool_soversion[1]
+)
+macos_darwin_versions = [
+  libtool_soversion[0] + 1,
+  '@0@.@1@'.format(libtool_soversion[0] + 1, libtool_soversion[1])
+]
 
 # Use these instead of meson.source_root() and meson.build_root() in subdirectories.
 # source_root() and build_root() are not useful, if this is a subproject.
diff --git a/skeletonmm/skeleton/skeletonmm/meson.build b/skeletonmm/skeleton/skeletonmm/meson.build
index db6327a..6049cce 100644
--- a/skeletonmm/skeleton/skeletonmm/meson.build
+++ b/skeletonmm/skeleton/skeletonmm/meson.build
@@ -2,7 +2,7 @@
 
 # Input: skeletonmm_build_dep, skeletonmm_pcname, maintainer_mode, project_source_root,
 #        generate_binding, m4_files, skeletonmm_libversion, install_includedir,
-#        python3
+#        macos_darwin_versions, python3
 # Output: hg_ccg_basenames, extra_h_files, built_h_file_targets, built_files_root,
 #         skeletonmm_dep
 
@@ -96,6 +96,7 @@ if maintainer_mode
   skeletonmm_library = library(skeletonmm_pcname,
     built_cc_file_targets, built_h_file_targets, extra_cc_files,
     version: skeletonmm_libversion,
+    darwin_versions: macos_darwin_versions,
     include_directories: extra_include_dirs,
     dependencies: skeletonmm_build_dep,
     install: true,
@@ -137,6 +138,7 @@ else # not maintainer_mode
   skeletonmm_library = library(skeletonmm_pcname,
     built_cc_files, extra_cc_files,
     version: skeletonmm_libversion,
+    darwin_versions: macos_darwin_versions,
     include_directories: extra_include_dirs,
     dependencies: skeletonmm_build_dep,
     install: true,