ci: increase cross compile parallel

The cross compile job isn't run that frequently, but when failures
happen it is very annoying to debug because the max-parallel setting
of 1 makes failures take a long time. Increasing to 2 is very helpful
here and doesn't tax CI too much.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Daniel Noland <daniel@githedgehog.com>

Author: daniel-noland

.github/workflows/dev.yml

@@ -565,7 +565,7 @@ jobs:
       USER: "runner"
     strategy:
       fail-fast: false
-      max-parallel: 1
+      max-parallel: 2
       matrix:
         platform:
           - "aarch64"