[ci][gcc] have gcc runs build with -Werror set

Be a bit more strict about what is accepted into mainline by building
with -Werror set for gcc builds.

Clang builds will get the same treatment soon.

Also turn off some ubsan compiles for some of the older arches where
there's very little value (and it probably doesn't work anyway).

.github/workflows/github-ci.yml

@@ -35,6 +35,15 @@ jobs:
           # no real point building ubsan on the old compiler
           - ubsan: 1
             toolchain-ver: 7.5.0
+          # do not build ubsan for older 32bit arches where it is not well supported
+          - ubsan: 1
+            arch: m68k
+          - ubsan: 1
+            arch: microblaze
+          - ubsan: 1
+            arch: mips
+          - ubsan: 1
+            arch: or1k
           # no toolchain for 7.5.0 for or1k
           - arch: or1k
             toolchain-ver: 7.5.0
@@ -147,7 +156,7 @@ jobs:
         export -n ARCH
         # DEBUG is passed through to the build script
         # UBSAN is passed through to the build script
-        ./scripts/buildall -a "${{ matrix.arch }}"
+        ./scripts/buildall -e -a "${{ matrix.arch }}"
 
     # upload artifacts
     #- uses: actions/upload-artifact@v2