[libgweather] build: Fixes cross-compilation of gir

[Bastien Nocera <hadess src gnome org>]

commit b8c66ca663bbb816419f084a75211f61aec84a2c
Author: maxice8 <thinkabit ukim gmail com>
Date:   Tue Feb 5 15:46:51 2019 -0200

    build: Fixes cross-compilation of gir
    
    Pass -DGWEATHER_COMPILATION to gir compiler
    
    In file included from /builddir/libgweather-3.28.2/build/libgweather/gweather-enum-types.h:12,
                     from /builddir/libgweather-3.28.2/build/g-ir-cpp-wmkyat6f.c:4:
    ./libgweather/gweather-version.h:28:2: error: #error "gweather-version.h must not be included 
individually, include gweather.h instead"
     #error "gweather-version.h must not be included individually, include gweather.h instead"
      ^~~~~
    In file included from /builddir/libgweather-3.28.2/build/g-ir-cpp-wmkyat6f.c:5:
    /builddir/libgweather-3.28.2/libgweather/gweather.h:25:2: error: #error "libgweather should only be used 
if you understand that it's subject to change, and is not supported as a fixed API/ABI or as part of the 
platform"
     #error "libgweather should only be used if you understand that it's subject to change, and is not 
supported as a fixed API/ABI or as part of the platform"
      ^~~~~
    Traceback (most recent call last):
      File "/usr/lib/python3.6/distutils/unixccompiler.py", line 107, in preprocess
        self.spawn(pp_args)
      File "/usr/lib/python3.6/distutils/ccompiler.py", line 909, in spawn
        spawn(cmd, dry_run=self.dry_run)
      File "/usr/lib/python3.6/distutils/spawn.py", line 36, in spawn
        _spawn_posix(cmd, search_path, dry_run=dry_run)
      File "/usr/lib/python3.6/distutils/spawn.py", line 159, in _spawn_posix
        % (cmd, exit_status))
    distutils.errors.DistutilsExecError: command 'aarch64-linux-gnu-cpp' failed with exit status 1

 libgweather/meson.build | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/libgweather/meson.build b/libgweather/meson.build
index 47a1547..301e7e8 100644
--- a/libgweather/meson.build
+++ b/libgweather/meson.build
@@ -75,7 +75,10 @@ gweather_gir = gnome.generate_gir(lib_libgweather,
   identifier_prefix: 'GWeather',
   export_packages: 'gweather-3.0',
   header: 'libgweather/gweather.h',
-  extra_args: ['--warn-all'],
+  extra_args: [
+    '--warn-all',
+    '-DGWEATHER_COMPILATION',
+  ],
   install: true,
 )