meson: fix install dir for generated header files

Nixos installs into a non-standard includedir, so need
to take account of the 'includedir' option instead of
just hard-coding 'include' here.

https://bugzilla.gnome.org/show_bug.cgi?id=794856

gst-libs/gst/app/meson.build

@@ -12,7 +12,7 @@ app_enums = gnome.mkenums_simple('app-enumtypes',
   header_prefix : '#include <gst/app/app-prelude.h>',
   decorator : 'GST_APP_API',
   install_header: true,
-  install_dir : 'include/gstreamer-1.0/gst/app/')
+  install_dir : join_paths(get_option('includedir'), 'gstreamer-1.0/gst/app'))
 gstapp_c = app_enums[0]
 gstapp_h = app_enums[1]
 

gst-libs/gst/audio/meson.build

@@ -67,7 +67,7 @@ audio_enums = gnome.mkenums_simple('audio-enumtypes',
   header_prefix : '#include <gst/audio/audio-prelude.h>',
   decorator : 'GST_AUDIO_API',
   install_header: true,
-  install_dir : 'include/gstreamer-1.0/gst/audio/')
+  install_dir : join_paths(get_option('includedir'), 'gstreamer-1.0/gst/audio'))
 gstaudio_c = audio_enums[0]
 gstaudio_h = audio_enums[1]
 

gst-libs/gst/pbutils/meson.build

@@ -19,7 +19,7 @@ pbconf.set('PACKAGE_VERSION_MICRO', gst_version_micro)
 pbconf.set('PACKAGE_VERSION_NANO', gst_version_nano)
 gst_pbutils_version_h = configure_file(input : 'gstpluginsbaseversion.h.in',
   output: 'gstpluginsbaseversion.h',
-  install_dir : 'include/gstreamer-1.0/gst/pbutils/',
+  install_dir : join_paths(get_option('includedir'), 'gstreamer-1.0/gst/pbutils'),
   configuration: pbconf)
 
 pbutils_headers = [
@@ -43,7 +43,7 @@ pbutils_enums = gnome.mkenums_simple('pbutils-enumtypes',
   header_prefix : '#include <gst/pbutils/pbutils-prelude.h>',
   decorator : 'GST_PBUTILS_API',
   install_header: true,
-  install_dir : 'include/gstreamer-1.0/gst/pbutils/')
+  install_dir : join_paths(get_option('includedir'), 'gstreamer-1.0/gst/pbutils'))
 gstpbutils_c = pbutils_enums[0]
 gstpbutils_h = pbutils_enums[1]
 

gst-libs/gst/rtp/meson.build

@@ -27,7 +27,7 @@ rtp_enums = gnome.mkenums_simple('gstrtp-enumtypes',
   header_prefix : '#include <gst/rtp/rtp-prelude.h>',
   decorator : 'GST_RTP_API',
   install_header: true,
-  install_dir : 'include/gstreamer-1.0/gst/rtp/')
+  install_dir : join_paths(get_option('includedir'), 'gstreamer-1.0/gst/rtp'))
 gstrtp_enum_c = rtp_enums[0]
 gstrtp_enum_h = rtp_enums[1]
 

gst-libs/gst/rtsp/meson.build

@@ -27,7 +27,7 @@ rtsp_enums = gnome.mkenums_simple('gstrtsp-enumtypes',
   header_prefix : '#include <gst/rtsp/rtsp-prelude.h>',
   decorator : 'GST_RTSP_API',
   install_header: true,
-  install_dir : 'include/gstreamer-1.0/gst/rtsp/')
+  install_dir : join_paths(get_option('includedir'), 'gstreamer-1.0/gst/rtsp'))
 gstrtsp_c = rtsp_enums[0]
 gstrtsp_h = rtsp_enums[1]
 

gst-libs/gst/tag/meson.build

@@ -31,7 +31,7 @@ tag_enums = gnome.mkenums_simple('tag-enumtypes',
   header_prefix : '#include <gst/tag/tag-prelude.h>',
   decorator : 'GST_TAG_API',
   install_header: true,
-  install_dir : 'include/gstreamer-1.0/gst/tag/')
+  install_dir : join_paths(get_option('includedir'), 'gstreamer-1.0/gst/tag'))
 gsttag_c = tag_enums[0]
 gsttag_h = tag_enums[1]
 tag_gen_sources = [gsttag_h]

gst-libs/gst/video/meson.build

@@ -92,7 +92,7 @@ video_enums = gnome.mkenums_simple('video-enumtypes',
   header_prefix : '#include <gst/video/video-prelude.h>',
   decorator : 'GST_VIDEO_API',
   install_header: true,
-  install_dir : 'include/gstreamer-1.0/gst/video/')
+  install_dir : join_paths(get_option('includedir'), 'gstreamer-1.0/gst/video'))
 gstvideo_c = video_enums[0]
 gstvideo_h = video_enums[1]
 video_gen_sources = [gstvideo_h]