Add manual build metadata generation outside of build process

Assets/BuildMetadata/Editor/BuildMetadataMenu.cs

@@ -0,0 +1,13 @@
+using UnityEditor;
+
+namespace BuildMetadata.Editor
+{
+    internal static class BuildMetadataMenu
+    {
+        [MenuItem("Tools/Build Metadata/Generate Now", priority = 100)]
+        private static void GenerateNow()
+        {
+            BuildMetadataProcessor.Generate();
+        }
+    }
+}

Assets/BuildMetadata/Editor/BuildMetadataProcessor.cs

@@ -25,7 +25,21 @@ public class BuildMetadataProcessor : IPreprocessBuildWithReport
         public void OnPreprocessBuild(BuildReport report)
         {
             var buildTargetGroup = BuildPipeline.GetBuildTargetGroup(report.summary.platform);
+            Generate(buildTargetGroup, report.summary.guid.ToString());
+        }
 
+        /// <summary>
+        /// Generates and writes the build metadata JSON using the active build target.
+        /// Can be called without starting a build.
+        /// </summary>
+        public static void Generate()
+        {
+            var buildTargetGroup = BuildPipeline.GetBuildTargetGroup(EditorUserBuildSettings.activeBuildTarget);
+            Generate(buildTargetGroup, Guid.NewGuid().ToString());
+        }
+
+        private static void Generate(BuildTargetGroup buildTargetGroup, string buildGuid)
+        {
             var data = new BuildMetadataData(
                 appVersion:         Application.version,
                 unityVersion:       Application.unityVersion,
@@ -41,7 +55,7 @@ public void OnPreprocessBuild(BuildReport report)
                 scriptingDefines:   PlayerSettings.GetScriptingDefineSymbolsForGroup(buildTargetGroup),
                 buildMachine:       Environment.MachineName,
                 buildOS:            Environment.OSVersion.ToString(),
-                buildGuid:          report.summary.guid.ToString()
+                buildGuid:          buildGuid
             );
 
             PopulateExtensions(data);