Made compilation error colors come through et.

tools/pkg/engine_build_configs/lib/src/build_config_runner.dart

@@ -5,7 +5,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:ffi' as ffi;
-import 'dart:io' as io show Directory, File, Process, ProcessResult;
+import 'dart:io' as io show Directory, File, Platform, Process, ProcessResult, stdout;
 import 'dart:math';
 
 import 'package:meta/meta.dart' show visibleForTesting;
@@ -565,6 +565,7 @@ final class BuildRunner extends Runner {
 
   static final RegExp _gccRegex =
       RegExp(r'^(.+)(:\d+:\d+:\s+(?:error|note|warning):\s+.*)$');
+  static final RegExp _ansiRegex = RegExp(r'\x1b\[[\d;]*m');
 
   /// Converts relative [path], who is relative to [dirPath] to a relative path
   /// of the `CWD`.
@@ -573,15 +574,22 @@ final class BuildRunner extends Runner {
     return './${p.relative(abs)}';
   }
 
+  static String _stripAnsi(String input) {
+    return input.replaceAll(_ansiRegex, '');
+  }
+
   /// Takes a [line] from compilation and makes the path relative to `CWD` where
   /// the paths are relative to [outDir].
   @visibleForTesting
   static String fixGccPaths(String line, String outDir) {
-    final Match? match = _gccRegex.firstMatch(line);
+    final sansAnsi = _stripAnsi(line);
+    final Match? match = _gccRegex.firstMatch(sansAnsi);
     if (match == null) {
       return line;
     } else {
-      return '${_makeRelative(match.group(1)!, outDir)}${match.group(2)}';
+      final String path = match.group(1)!;
+      final String fixedPath = _makeRelative(match.group(1)!, outDir);
+      return line.replaceFirst(path, fixedPath);
     }
   }
 
@@ -625,10 +633,16 @@ final class BuildRunner extends Runner {
       if (dryRun) {
         processResult = _dryRunResult;
       } else {
+        final bool shouldEmitAnsi =
+            (io.stdout.supportsAnsiEscapes && io.Platform.environment['CLICOLOR_FORCE'] != '0') ||
+            io.Platform.environment['CLICOLOR_FORCE'] == '1';
         final io.Process process = await processRunner.processManager.start(
           command,
           workingDirectory: engineSrcDir.path,
-          environment: rbeConfig.environment,
+          environment: {
+            ...rbeConfig.environment,
+            if (shouldEmitAnsi) 'CLICOLOR_FORCE': '1',
+          }
         );
         final List<int> stderrOutput = <int>[];
         final List<int> stdoutOutput = <int>[];

tools/pkg/engine_build_configs/test/build_config_runner_test.dart

@@ -539,6 +539,35 @@ void main() {
     expect(fixed, './$error');
   });
 
+  test('fixes gcc paths with ansi colors', () {
+    final String outDir = path.join(io.Directory.current.path, 'foo', 'bar');
+    // An error string with ANSI escape codes for colors.
+    final List<int> bytes = [
+      27, 91, 49, 109, 46, 46, 47, 46, 46, 47, 102, //
+      108, 117, 116, 116, 101, 114, 47, 105, 109, 112, 101, 108, 108, 101, //
+      114, 47, 100, 105, 115, 112, 108, 97, 121, 95, 108, 105, 115, 116, 47, //
+      100, 108, 95, 100, 105, 115, 112, 97, 116, 99, 104, 101, 114, 46, 99, //
+      99, 58, 55, 51, 52, 58, 55, 58, 32, 27, 91, 48, 109, 27, 91, 48, 59, //
+      49, 59, 51, 49, 109, 101, 114, 114, 111, 114, 58, 32, 27, 91, 48, 109, //
+      27, 91, 49, 109, 117, 115, 101, 32, 111, 102, 32, 117, 110, 100, 101, //
+      99, 108, 97, 114, 101, 100, 32, 105, 100, 101, 110, 116, 105, 102, 105, //
+      101, 114, 32, 39, 114, 111, 99, 107, 101, 116, 39, 27, 91, 48, 109,
+    ];
+    final String error = convert.utf8.decode(bytes);
+    final String fixed = BuildRunner.fixGccPaths(error, outDir);
+    expect(
+      fixed.contains('../../flutter/impeller/display_list/dl_dispatcher.cc'),
+      isFalse,
+      reason: 'Fixed string: $fixed',
+    );
+    expect(
+      fixed.contains('./flutter/impeller/display_list/dl_dispatcher.cc'),
+      isTrue,
+      reason: 'Fixed string: $fixed',
+    );
+    expect(fixed[0], '\x1B', reason: 'Fixed string: $fixed');
+  });
+
   test('GlobalBuildRunner skips generators when runGenerators is false',
       () async {
     final Build targetBuild = buildConfig.builds[0];