programs: port mesa_shader_cache persistors over to sandbox.mesaCacheDir

hosts/common/programs/gnome-contacts.nix

@@ -29,9 +29,8 @@
       did-initial-setup = true;
     };
 
-    sandbox.extraHomePaths = [
-      ".cache/mesa_shader_cache_db"  #< else it takes too long to load and shows a misleading error message
-    ];
+    # if shaders are NOT persisted, then gnome-contacts takes too long to load and shows a misleading error message
+    sandbox.mesaCacheDir = ".cache/gnome-contacts/mesa_shader_cache_db";
 
     sandbox.whitelistDbus = [ "user" ];  #< for OpenURI, evolution-data-server
     sandbox.whitelistDri = true;  #< speculative, but i'd like it to be responsive on mobile

hosts/common/programs/megapixels-next.nix

@@ -46,7 +46,6 @@ in
     sandbox.whitelistDbus = [ "user" ];  #< so that it can open the image viewer using fdo portal...
     sandbox.extraHomePaths = [
       # ".config/megapixels"
-      ".cache/mesa_shader_cache_db"  # loads way faster
       "Pictures/Photos"
       # also it addresses a lot via relative path.
     ];
@@ -56,6 +55,7 @@ in
       "/sys/class/leds"  #< for flash, presumably
     ];
     sandbox.whitelistAvDev = true;
+    sandbox.mesaCacheDir = ".cache/megapixels/mesa_shader_cache_db";  # loads WAY faster
     gsettings."me/gapixels/megapixels" = {
       # **required** for it to find its postprocess script
       postprocessor = "${cfg.package}/share/megapixels/postprocess.sh";

hosts/common/programs/megapixels.nix

@@ -31,7 +31,6 @@
     sandbox.whitelistDbus = [ "user" ];  #< so that it can in theory open the image viewer using fdo portal... but it doesn't :|
     sandbox.extraHomePaths = [
       # ".config/megapixels"
-      ".cache/mesa_shader_cache_db"  # loads way faster
       "Pictures/Photos"
       # also it addresses a lot via relative path.
     ];
@@ -41,6 +40,7 @@
       "/sys/class/leds"  #< for flash, presumably
     ];
     sandbox.whitelistAvDev = true;
+    sandbox.mesaCacheDir = ".cache/megapixels/mesa_shader_cache_db";  # loads WAY faster
     gsettingsPersist = [
       "org/postmarketos/megapixels"  #< needs to set `postprocessor` else it will segfault during post-process
     ];