Simplify the Meson now that upstream bug is fixed

Upstream bug is https://github.com/mesonbuild/meson/issues/13584.

This PR will fail for now, but eventually after Meson is bumped in
Nixpkgs, it will succeed.

src/libstore/meson.build

@@ -352,13 +352,7 @@ libraries_private = []
 
 extra_pkg_config_variables = {
   'storedir' : get_option('store-dir'),
+  'localstatedir' : get_option('localstatedir'),
 }
 
-# Working around https://github.com/mesonbuild/meson/issues/13584
-if host_machine.system() != 'darwin'
-  extra_pkg_config_variables += {
-    'localstatedir' : get_option('localstatedir'),
-  }
-endif
-
 subdir('nix-meson-build-support/export')

src/nix/meson.build

@@ -5,7 +5,6 @@ project('nix', 'cpp',
     # TODO(Qyriad): increase the warning level
     'warning_level=1',
     'errorlogs=true', # Please print logs for tests that fail
-    'localstatedir=/nix/var',
   ],
   meson_version : '>= 1.4',
   license : 'LGPL-2.1-or-later',
@@ -249,11 +248,7 @@ custom_target(
 # TODO(Ericson3214): Dosen't yet work
 #meson.override_find_program(linkname, t)
 
-localstatedir = nix_store.get_variable(
-  'localstatedir',
-  default_value : get_option('localstatedir'),
-)
-assert(localstatedir == get_option('localstatedir'))
+localstatedir = nix_store.get_variable('localstatedir')
 store_dir = nix_store.get_variable('storedir')
 subdir('scripts')
 subdir('misc')