gnu: meson: Update to 0.50.0.

* gnu/packages/build-tools.scm (meson): Update to 0.50.0.
* gnu/packages/patches/at-spi2-core-meson-compat.patch,
gnu/packages/patches/totem-meson-compat.patch: New files.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/gnome.scm (totem)[source](patches): Add totem-meson.compat.patch.
* gnu/packages/gtk.scm (at-spi2-core)[source](patches): New field.

gnu/local.mk

@@ -652,6 +652,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/apr-skip-getservbyname-test.patch	\
   %D%/packages/patches/aria2-CVE-2019-3500.patch		\
   %D%/packages/patches/aspell-default-dict-dir.patch		\
+  %D%/packages/patches/at-spi2-core-meson-compat.patch		\
   %D%/packages/patches/ath9k-htc-firmware-binutils.patch	\
   %D%/packages/patches/ath9k-htc-firmware-gcc.patch		\
   %D%/packages/patches/ath9k-htc-firmware-objcopy.patch		\
@@ -1287,6 +1288,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/tk-find-library.patch			\
   %D%/packages/patches/ttf2eot-cstddef.patch			\
   %D%/packages/patches/ttfautohint-source-date-epoch.patch	\
+  %D%/packages/patches/totem-meson-compat.patch			\
   %D%/packages/patches/totem-meson-easy-codec.patch		\
   %D%/packages/patches/tuxpaint-stamps-path.patch		\
   %D%/packages/patches/twinkle-include-qregexpvalidator.patch	\

gnu/packages/build-tools.scm

@@ -160,7 +160,7 @@ files and generates build instructions for the Ninja build system.")
 (define-public meson
   (package
     (name "meson")
-    (version "0.49.2")
+    (version "0.50.0")
     (source (origin
               (method url-fetch)
               (uri (string-append "https://github.com/mesonbuild/meson/"
@@ -168,7 +168,7 @@ files and generates build instructions for the Ninja build system.")
                                   version ".tar.gz"))
               (sha256
                (base32
-                "1z89f71r29laywx75bamjakybv9653wz0vd2l4xhvqy1dqr197zg"))))
+                "07q2wz23wjfk8z66mli1cc9as0ycjp5f39fd4awny82qv8nw86ra"))))
     (build-system python-build-system)
     (arguments
      `(;; FIXME: Tests require many additional inputs, a fix for the RUNPATH

gnu/packages/gnome.scm

@@ -3766,7 +3766,8 @@ for application developers.")
        (sha256
         (base32
          "1llyisls3pzf5bwkpxyfyxc2d3gpa09n5pjy7qsjdqrp3ya4k36g"))
-       (patches (search-patches "totem-meson-easy-codec.patch"))))
+       (patches (search-patches "totem-meson-easy-codec.patch"
+                                "totem-meson-compat.patch"))))
     (build-system meson-build-system)
     (native-inputs
      `(("pkg-config" ,pkg-config)

gnu/packages/gtk.scm

@@ -561,6 +561,7 @@ in the GNOME project.")
             (uri (string-append "mirror://gnome/sources/" name "/"
                                 (version-major+minor version)  "/"
                                 name "-" version ".tar.xz"))
+            (patches (search-patches "at-spi2-core-meson-compat.patch"))
             (sha256
              (base32
               "083j1v7kdjrpjsv1b9dl3d8xqj39jyp4cfn8i9gbbm7q2g93b923"))))

gnu/packages/patches/at-spi2-core-meson-compat.patch

@@ -0,0 +1,18 @@
+Fix build with Meson 0.50.0 and above.
+
+Taken from upstream repository:
+https://gitlab.gnome.org/GNOME/at-spi2-core/commit/44a812ea51223d82f21a098a2d45fcc5c329ce7a
+
+diff --git a/atspi/meson.build b/atspi/meson.build
+index b7a9357df1c4857dffa2ec123cd3073e67a07fea..2a6915d76202dabf923b50e6a8b85cbb83cb43d0 100644
+--- a/atspi/meson.build
++++ b/atspi/meson.build
+@@ -57,7 +57,7 @@ atspi_headers = [
+ 
+ atspi_includedir = join_paths(get_option('prefix'), get_option('includedir'), 'at-spi-2.0', 'atspi')
+ 
+-install_headers(atspi_headers, subdir: atspi_includedir)
++install_headers(atspi_headers, install_dir: atspi_includedir)
+ 
+ atspi_enums = gnome.mkenums('atspi-enum-types',
+                             sources: [ 'atspi-constants.h', 'atspi-types.h' ],

gnu/packages/patches/totem-meson-compat.patch

@@ -0,0 +1,14 @@
+Fix an error that occurs with Meson 0.50.0 and later:
+"ERROR: Subdir keyword must not be an absolute path".
+
+--- a/src/meson.build	2019-03-15 00:10:26.882293850 +0100
++++ b/src/meson.build	2019-03-15 00:10:54.312197229 +0100
+@@ -82,7 +82,7 @@
+ 
+ install_headers(
+   headers,
+-  subdir: join_paths(totem_includedir, totem_api_path)
++  install_dir: join_paths(totem_includedir, totem_api_path)
+ )
+ 
+ libtotem_player_sources = files(