meson: allow setting of custom pc variables

this brings the theme directory to the elementary .pc file.

Differential Revision: https://phab.enlightenment.org/D7224

meson.build

@@ -241,6 +241,8 @@ foreach package : subprojects
     pub_eo_file_target = []
     #private eo files target - never use this :)
     priv_eo_file_target = []
+    #use this variable to store custom variables in that should be placed in the .pc file
+    package_pc_variables = []
 
     foreach static_lib : package[9]
       if get_variable(static_lib, tmp_empty) == tmp_empty
@@ -290,6 +292,7 @@ foreach package : subprojects
         version : version_major + '.' + version_minor,
         libraries : tmp_pub_deps,
         requires : package[8],
+        variables : package_pc_variables
       )
       if package_name == 'ethumb_client'
         pkgconfig.generate(tmp_lib,

src/lib/elementary/meson.build

@@ -970,3 +970,5 @@ install_headers(elementary_header_src,
 )
 
 elementary_config_dir = include_directories('.')
+
+package_pc_variables = ['themes='+join_paths(dir_data, package_name, 'themes')]