fix: lazy fetch checksums for toolchains (#648)

Signed-off-by: Thulio Ferraz Assis <3149049+f0rmiga@users.noreply.github.com>

python/versions.bzl

diff --git a/python/versions.bzl b/python/versions.bzl
index a99e371..23bc1c3 100644
--- a/python/versions.bzl
+++ b/python/versions.bzl
@@ -122,11 +122,13 @@
         srcs = [],
         outs = ["print_toolchains_checksums.sh"],
         cmd = """\
-cat > "$@" <<EOF
+cat > "$@" <<'EOF'
 #!/bin/bash
 
 set -o errexit -o nounset -o pipefail
 
+echo "Fetching hashes..."
+
 {commands}
 EOF
         """.format(