github: workflows: build this PR against PR 51771 in Zephyr

Temporarily build this PR against zephyrproject-rtos/zephyr#51771
until that pull has been accepted to main.

Signed-off-by: Chris Friedt <cfriedt@meta.com>

.github/workflows/build.yml

@@ -48,7 +48,9 @@ jobs:
         run: |
           pip3 install -U west
           west init zephyrproject
-          cd zephyrproject
+          cd zephyrproject/zephyr
+          git fetch origin pull/51771/head:temp
+          git checkout temp
           west update $WEST_MODULES
 
       - name: Checkout Thrift Module