Add --dart-define, -D to assemble, deprecate --define, -d. (flutter#172510)

Closes flutter#98593.
Towards flutter#97505.

Author: matanlurey

packages/flutter_tools/lib/src/commands/assemble.dart

@@ -98,8 +98,16 @@ class AssembleCommand extends FlutterCommand {
       'define',
       abbr: 'd',
       valueHelp: 'target=key=value',
-      help: 'Allows passing configuration to a target, as in "--define=target=key=value".',
+      hide: !verboseHelp,
+      help:
+          'DEPRECATED. Use "--dart-define" or "-D" instead for consistency.\n'
+          '\n'
+          'Allows passing configuration to a target, as in "--define=target=key=value".',
     );
+
+    // New -D/--dart-define (consistent across app)
+    usesDartDefineOption();
+
     argParser.addOption(
       'performance-measurement-file',
       help: 'Output individual target performance to a JSON file.',
@@ -143,7 +151,6 @@ class AssembleCommand extends FlutterCommand {
           'root of the current Flutter project.',
     );
     usesExtraDartFlagOptions(verboseHelp: verboseHelp);
-    usesDartDefineOption();
     argParser.addOption(
       'resource-pool-size',
       help: 'The maximum number of concurrent tasks the build system will run.',
@@ -249,7 +256,7 @@ class AssembleCommand extends FlutterCommand {
           .childDirectory('flutter_build'),
       projectDir: _flutterProject.directory,
       packageConfigPath: packageConfigPath(),
-      defines: _parseDefines(stringsArg('define')),
+      defines: _parseDefines([...stringsArg('define'), ...stringsArg('dart-define')]),
       inputs: _parseDefines(stringsArg('input')),
       cacheDir: globals.cache.getRoot(),
       flutterRootDir: globals.fs.directory(Cache.flutterRoot),

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -757,6 +757,7 @@ abstract class FlutterCommand extends Command<void> {
   void usesDartDefineOption() {
     argParser.addMultiOption(
       FlutterOptions.kDartDefinesOption,
+      abbr: 'D',
       aliases: <String>[kDartDefines], // supported for historical reasons
       help:
           'Additional key-value pairs that will be available as constants '

packages/flutter_tools/test/commands.shard/hermetic/assemble_test.dart

@@ -232,7 +232,7 @@ void main() {
         'assemble',
         '--output',
         'Output',
-        '--DartDefines=flutter.inspector.structuredErrors%3Dtrue',
+        '-DartDefines=flutter.inspector.structuredErrors%3Dtrue',
         'debug_macos_bundle_flutter_assets',
       ];
       expect(