chore: add Cross.toml configuration for Steam Deck builds

Author: matthewjberger

CROSS.toml

@@ -0,0 +1,17 @@
+[build.env]
+passthrough = [
+    "PKG_CONFIG_ALLOW_CROSS=1",
+]
+
+[target.x86_64-unknown-linux-gnu]
+pre-build = [
+    "dpkg --add-architecture amd64",
+    "apt-get update",
+    "apt-get install -y pkg-config libvulkan-dev:amd64 libwayland-dev:amd64 libxkbcommon-dev:amd64 libx11-dev:amd64 libxcb1-dev:amd64 libxcb-render0-dev:amd64 libxcb-shape0-dev:amd64 libxcb-xfixes0-dev:amd64 libudev-dev:amd64",
+]
+
+[target.x86_64-unknown-linux-gnu.env]
+passthrough = [
+    "PKG_CONFIG_PATH=/usr/lib/x86_64-linux-gnu/pkgconfig",
+    "PKG_CONFIG_ALLOW_CROSS=1",
+]