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