ci: Abort autotools builds in case of unsupported options

Abort autotools CI builds in case we give them an unsupported
option. The default is to only warn, but the CI should catch
mistakes.

.github/workflows/build.yml

@@ -63,6 +63,7 @@ jobs:
           mkdir _ambuild && cd _ambuild
 
           ../src/configure
+          --enable-option-checking=fatal
           --enable-doc
           --enable-parport
           --enable-linuxgpio
@@ -312,6 +313,7 @@ jobs:
           CFLAGS="-I/opt/homebrew/include -I/opt/homebrew/opt/flex/include"
           LDFLAGS="-L/opt/homebrew/lib    -L/opt/homebrew/opt/bison/lib"
           ../src/configure
+          --enable-option-checking=fatal
 
       - name: Build
         run: make -C _ambuild -j$(nproc)