fast-build mode: use termux_download function for downloading 'Release'

Addition for cada4be0d8.

Release file may not exist too when metadata generation is in progress,
so we may need to do several tries to download file.

scripts/build/termux_get_repo_files.sh

@@ -21,8 +21,7 @@ termux_get_repo_files() {
 			local TERMUX_REPO_NAME=$(echo ${TERMUX_REPO_URL[$idx-1]} | sed -e 's%https://%%g' -e 's%http://%%g' -e 's%/%-%g')
 			local RELEASE_FILE=${TERMUX_COMMON_CACHEDIR}/${TERMUX_REPO_NAME}-${TERMUX_REPO_DISTRIBUTION[$idx-1]}-Release
 
-			curl --fail -L "${TERMUX_REPO_URL[$idx-1]}/dists/${TERMUX_REPO_DISTRIBUTION[$idx-1]}/Release" -o $RELEASE_FILE \
-			    || termux_error_exit "Download of InRelease and Release.gpg from ${TERMUX_REPO_URL[$idx-1]}/dists/${TERMUX_REPO_DISTRIBUTION[$idx-1]} failed"
+			termux_download "${TERMUX_REPO_URL[$idx-1]}/dists/${TERMUX_REPO_DISTRIBUTION[$idx-1]}/Release" $RELEASE_FILE "SKIP_CHECKSUM"
 
 			for arch in all $TERMUX_ARCH; do
 				local PACKAGES_HASH=$(./scripts/get_hash_from_file.py ${RELEASE_FILE} $arch ${TERMUX_REPO_COMPONENT[$idx-1]})