build: Disable fast failing for build actions

nightly / beta are not required actions but if they fail then all other
builds will be cancelled and so prevent the PR from being cleared as
buildable.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

.github/workflows/build.yaml

@@ -7,6 +7,7 @@ jobs:
     name: Build
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
         rust:
           - stable