CI: Adjust timeout multiplier to match twister

The philosopher test seems to run in real time on qemu, and ends up
taking just about a minute, the default timeout.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

.github/workflows/build.yml

@@ -76,4 +76,5 @@ jobs:
           df -h
 
           west twister -M all -T samples -T tests -v --inline-logs --integration -j 4 \
+             --timeout-multiplier 2 \
              $(cat etc/platforms.txt)