Add FreeBSD testing

Note that we can't do bundle creation on FreeBSD, since our `lldb` can't
read the core dump to figure out which libraries were loaded.  So we
just disallow `create_bundle` on FreeBSD.

Author: staticfloat

.buildkite/pipeline.yml

@@ -214,6 +214,24 @@ steps:
       os: "macos"
       arch: "x86_64"
 
+  - label: ":freebsd: :boom: FreeBSD coredumps"
+    plugins:
+      - ".buildkite/plugins/coreupload":
+          core_pattern: "**/*.core"
+          compressor: "zstd"
+          lldb_commands:
+            - "bt"
+    commands: |
+      # Enable core dumping
+      ulimit -c unlimited
+
+      # Create a sub-bash and kill it, then ignore its failure
+      mkdir foo && cd foo
+      bash -c 'kill -11 $$$$' || true
+    agents:
+      queue: "juliaecosystem"
+      os: "freebsd"
+      arch: "x86_64"
 
   - wait: ~
 

lib/common.sh

@@ -40,6 +40,12 @@ if [[ ! -v "BUILDKITE_PLUGIN_COREUPLOAD_DEBUGGER" ]]; then
     fi
 fi
 
+# If we're on FreeBSD, disable `CREATE_BUNDLE`:
+if [[ $(uname 2>/dev/null) == "FreeBSD" ]] && [[ "${CREATE_BUNDLE}" == "true" ]]; then
+    die "Cannot use 'create_bundle: true' on FreeBSD!"
+fi
+    
+
 # Check for compressor tools
 ensure_tool "tar" "needed to compress "
 if [[ "${COMPRESSOR}" == "zstd" ]]; then