build: Bump MSRV to 1.77.0

The ability to control the rustc flags (required for adding new
attributes to the allowed list of #[cfg(..)]) requires bumping the MSRV
to 1.77.0

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

.github/workflows/build.yaml

@@ -15,7 +15,7 @@ jobs:
           - stable
           - beta
           - nightly
-          - "1.74.1"
+          - "1.77.0"
         target:
           - x86_64-unknown-linux-gnu
           - x86_64-unknown-linux-musl

.github/workflows/docker-image.yaml

@@ -41,7 +41,7 @@ jobs:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           # generate Docker tags based on the following events/attributes
           tags: |
-            type=raw,value=20240407-0
+            type=raw,value=20240507-0
             type=sha
 
       - name: Build and push