Change command to to be compatible with alpine distros. (#227)

Replaces #198 and closes #197

action.yml

@@ -132,7 +132,7 @@ runs:
         fi
 
         # Try to verify the downloaded binary
-        if ! grep coveralls-linux.tar.gz coveralls-checksums.txt | sha256sum --check; then
+        if ! grep coveralls-linux.tar.gz coveralls-checksums.txt | sha256sum -c; then
           echo "Checksum verification failed (Linux)."
           [ "${{ inputs.fail-on-error }}" == "false" ] && exit 0
           exit 1