ci: run tests with RUST_BACKTRACE=1

Produces backtraces which would allow some initial debugging on hard to
find issues.

Part-of: <gstreamer/gst-plugins-rs!1606>

.gitlab-ci.yml

@@ -99,11 +99,11 @@ trigger:
     - rustc --version
 
     - cargo build --locked --color=always --workspace --all-targets
-    - G_DEBUG=fatal_warnings cargo test --locked --color=always --workspace --all-targets
+    - RUST_BACKTRACE=1 G_DEBUG=fatal_warnings cargo test --locked --color=always --workspace --all-targets
     - cargo build --locked --color=always --workspace --all-targets --all-features --exclude gst-plugin-gtk4
-    - G_DEBUG=fatal_warnings cargo test --locked --color=always --workspace --all-targets --all-features --exclude gst-plugin-gtk4
+    - RUST_BACKTRACE=1 G_DEBUG=fatal_warnings cargo test --locked --color=always --workspace --all-targets --all-features --exclude gst-plugin-gtk4
     - cargo build --locked --color=always --workspace --all-targets --no-default-features
-    - G_DEBUG=fatal_warnings cargo test --locked --color=always --workspace --all-targets --no-default-features
+    - RUST_BACKTRACE=1 G_DEBUG=fatal_warnings cargo test --locked --color=always --workspace --all-targets --no-default-features
 
 test msrv:
   extends:

ci/run_windows_tests.ps1

@@ -36,6 +36,7 @@ function Run-Tests {
     }
 
     $env:G_DEBUG="fatal_warnings"
+    $env:RUST_BACKTRACE="1"
     cargo test --no-fail-fast --color=always --workspace $local_exclude --all-targets $Features
 
     if (!$?) {