The ebuild installs gettext catalogs under /usr/share/locale. Use that
directory for non-Flatpak builds instead of the build-time source tree,
which is not available after installation.

diff --git a/src/config.rs b/src/config.rs
--- a/src/config.rs
+++ b/src/config.rs
@@ -1,7 +1,7 @@
 pub const DATA_DIR: &str = "stremio";
 
 pub const GETTEXT_DOMAIN: &str = "stremio";
-pub const GETTEXT_DIR_DEV: &str = concat!(env!("CARGO_MANIFEST_DIR"), "/po");
+pub const GETTEXT_DIR_DEV: &str = "/usr/share/locale";
 pub const GETTEXT_DIR_FLATPAK: &str = "/app/share/locale";
 
 pub const STARTUP_URL: &str = "http://127.0.0.1:11470/proxy/d=https%3A%2F%2Fweb.stremio.com/";