ci: Show memory layout

I regularly use the `.mem` file to determine the impact changes have on
the RAM and flash usage. Print it as part of CI so I can easily see it
for all boards.

Signed-off-by: Tim Crawford <tcrawford@system76.com>

.github/workflows/ci.yml

@@ -61,3 +61,7 @@ jobs:
 
       - name: Build firmware
         run: make BOARD=${{ matrix.boards }} VERBOSE=1
+
+      - name: Show memory layout
+        run: cat build/ec.mem
+        continue-on-error: true