meson: add global defines using add_project_arguments()

We're not going to be compiling any other C code, so let's simplify
this.

Author: keszybz

meson.build

@@ -15,9 +15,10 @@ python_dep = python.dependency()
 
 libsystemd_dep = dependency('libsystemd')
 
-common_c_args = [
+add_project_arguments(
         '-DPACKAGE_VERSION="@0@"'.format(meson.project_version()),
         '-DLIBSYSTEMD_VERSION=@0@'.format(libsystemd_dep.version()),
-]
+        language : 'c',
+)
 
 subdir('src/systemd')

src/systemd/meson.build

@@ -5,7 +5,6 @@ python.extension_module(
         '_journal',
         ['_journal.c', 'pyutil.c'],
         dependencies: [libsystemd_dep],
-        c_args: common_c_args,
         install: true,
         subdir: 'systemd',
 )
@@ -15,7 +14,6 @@ python.extension_module(
         '_reader',
         ['_reader.c', 'pyutil.c', 'strv.c'],
         dependencies: [libsystemd_dep],
-        c_args: common_c_args,
         install: true,
         subdir: 'systemd',
 )
@@ -25,7 +23,6 @@ python.extension_module(
         '_daemon',
         ['_daemon.c', 'pyutil.c', 'util.c'],
         dependencies: [libsystemd_dep],
-        c_args: common_c_args,
         install: true,
         subdir: 'systemd',
 )
@@ -35,7 +32,6 @@ python.extension_module(
         'id128',
         ['id128.c', 'pyutil.c'],
         dependencies: [libsystemd_dep],
-        c_args: common_c_args,
         install: true,
         subdir: 'systemd',
 )
@@ -45,7 +41,6 @@ python.extension_module(
         'login',
         ['login.c', 'pyutil.c', 'strv.c'],
         dependencies: [libsystemd_dep],
-        c_args: common_c_args,
         install: true,
         subdir: 'systemd',
 )