510 - SBOM attestation stdout (#785)

add syft attest command to produce an attestation as application/vnd.in-toto+json to standard out using on disk PKI

Signed-off-by: Christopher Phillips <christopher.phillips@anchore.com>

.github/workflows/validations.yaml

@@ -348,9 +348,16 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-go-${{ env.GO_VERSION }}-
 
-      - name: (cache-miss) Bootstrap go dependencies
-        if: steps.go-cache.outputs.cache-hit != 'true'
-        run: make bootstrap-go
+      - name: Restore tool cache
+        id: tool-cache
+        uses: actions/cache@v2.1.3
+        with:
+          path: ${{ github.workspace }}/.tmp
+          key: ${{ runner.os }}-tool-${{ hashFiles('Makefile') }}
+
+      - name: (cache-miss) Bootstrap all project dependencies
+        if: steps.tool-cache.outputs.cache-hit != 'true' || steps.go-cache.outputs.cache-hit != 'true'
+        run: make bootstrap
 
       - name: Build key for tar cache
         run: make cli-fingerprint