m/test/swptm/certtool: init

This implements a minimal GnuTLS certtool replacement. It will be used
by swtpm_setup and friends when generating an emulated TPM certificate.

Change-Id: I7635ccdc50459fec9287ea790488e110c6ce3094
Reviewed-on: https://review.monogon.dev/c/monogon/+/3128
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/test/swtpm/certtool/BUILD.bazel b/metropolis/test/swtpm/certtool/BUILD.bazel
new file mode 100644
index 0000000..b017ed8
--- /dev/null
+++ b/metropolis/test/swtpm/certtool/BUILD.bazel
@@ -0,0 +1,15 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")
+
+go_library(
+    name = "certtool_lib",
+    srcs = ["main.go"],
+    importpath = "source.monogon.dev/metropolis/test/swtpm/certtool",
+    visibility = ["//visibility:private"],
+    deps = ["@com_github_spf13_pflag//:pflag"],
+)
+
+go_binary(
+    name = "certtool",
+    embed = [":certtool_lib"],
+    visibility = ["//visibility:public"],
+)