workflows: Increase timeout for toolchain install

5 minutes seems to be failing on a regular basis, so
increase it.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

Author: 6by9

.github/workflows/kernel-build.yml

@@ -67,7 +67,7 @@ jobs:
         else
           sudo apt-get install gcc-arm-linux-gnueabihf;
         fi
-      timeout-minutes: 5
+      timeout-minutes: 15
 
     - uses: actions/checkout@v4
       with: