Fix release archive format

Author: calebzulawski

.github/workflows/release_prep.sh

@@ -5,4 +5,4 @@ set -o errexit -o nounset -o pipefail
 TAG=$1
 PREFIX="portable_cc_toolchain-${TAG:1}"
 ARCHIVE="bazel_portable_cc_toolchain-$TAG.tar.gz"
-git archive --format=tar --prefix=${PREFIX}/ ${TAG}:bazel --output=${ARCHIVE}
+git archive --format=tar --prefix=${PREFIX}/ ${TAG}:bazel | gzip > ${ARCHIVE}