test omicron-common can be built externally

.github/buildomat/jobs/omicron-common-helios.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+#:
+#: name = "omicron-common (helios)"
+#: variety = "basic"
+#: target = "helios-2.0"
+#: rust_toolchain = "1.77.2"
+#: output_rules = []
+
+exec .github/buildomat/omicron-common.sh

.github/buildomat/jobs/omicron-common-linux.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+#:
+#: name = "omicron-common (ubuntu-22.04)"
+#: variety = "basic"
+#: target = "ubuntu-22.04"
+#: rust_toolchain = "1.77.2"
+#: output_rules = []
+
+sudo apt-get update
+sudo apt-get install -y libssl-dev pkg-config
+
+exec .github/buildomat/omicron-common.sh

.github/buildomat/omicron-common.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+
+# Verify that omicron-common builds successfully when used as a dependency
+# in an external project. It must not leak anything that requires an external
+# dependency (apart from OpenSSL/pkg-config).
+
+set -o errexit
+set -o pipefail
+set -o xtrace
+
+cargo --version
+rustc --version
+
+cargo new --lib test-project
+cd test-project
+cargo add omicron-common \
+    --git https://github.com/oxidecomputer/omicron.git \
+    --rev "$GITHUB_SHA"
+cargo check
+cargo build --release