Add open Shorebird CI and release tooling

scripts/verify_engine_args.sh

@@ -0,0 +1,84 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+if [[ "$#" -eq 0 ]]; then
+  echo "usage: $0 <args.gn>... | <args.gn> key=value ..." >&2
+  exit 64
+fi
+
+verify_no_ddm() {
+  local args_file="$1"
+
+  if [[ ! -f "$args_file" ]]; then
+    echo "missing args.gn: $args_file" >&2
+    exit 66
+  fi
+
+  local actual
+  if ! actual="$(read_gn_value "$args_file" dart_dynamic_modules)"; then
+    return 0
+  fi
+  if [[ "$actual" == "true" ]]; then
+    echo "DART_DYNAMIC_MODULES must not be enabled: $args_file" >&2
+    exit 70
+  fi
+}
+
+read_gn_value() {
+  local file="$1"
+  local key="$2"
+  awk -v key="$key" '
+    $1 == key && $2 == "=" {
+      value = $0
+      sub("^[[:space:]]*" key "[[:space:]]*=[[:space:]]*", "", value)
+      sub("[[:space:]]*$", "", value)
+      found = 1
+    }
+    END {
+      if (!found) {
+        exit 1
+      }
+      print value
+    }
+  ' "$file"
+}
+
+has_expectations=0
+for arg in "$@"; do
+  if [[ "$arg" == *=* ]]; then
+    has_expectations=1
+    break
+  fi
+done
+
+if [[ "$has_expectations" == "0" ]]; then
+  for args_file in "$@"; do
+    verify_no_ddm "$args_file"
+    echo "Verified $args_file: dart_dynamic_modules is not true"
+  done
+  exit 0
+fi
+
+args_file="$1"
+shift
+verify_no_ddm "$args_file"
+
+for expectation in "$@"; do
+  if [[ "$expectation" != *=* ]]; then
+    echo "invalid expectation: $expectation; expected key=value" >&2
+    exit 64
+  fi
+
+  key="${expectation%%=*}"
+  value="${expectation#*=}"
+  if ! actual="$(read_gn_value "$args_file" "$key")"; then
+    echo "expected $key = $value in $args_file, but $key is missing" >&2
+    exit 70
+  fi
+  if [[ "$actual" != "$value" ]]; then
+    echo "expected $key = $value in $args_file, found $actual" >&2
+    exit 70
+  fi
+done
+
+echo "Verified $args_file: dart_dynamic_modules is not true and expected flags are present"