Made building with asan work

ci/builders/mac_unopt.json

@@ -514,6 +514,49 @@
                 }
             }
         },
+        {
+            "cas_archive": false,
+            "drone_dimensions":
+            [
+                "os=Mac-13|Mac-14",
+                "device_type=none",
+                "cpu=arm64"
+            ],
+            "gclient_variables":
+            {
+                "download_android_deps": false,
+                "use_rbe": true
+            },
+            "gn":
+            [
+                "--target-dir",
+                "ci/host_debug_unopt_arm64",
+                "--runtime-mode",
+                "debug",
+                "--unoptimized",
+                "--no-stripped",
+                "--no-lto",
+                "--xcode-symlinks",
+                "--asan",
+                "--rbe",
+                "--no-goma"
+            ],
+            "name": "ci/macos/host_debug_unopt_asan",
+            "description": "Builds impeller golden unit tests with asan enabled.",
+            "ninja":
+            {
+                "config": "ci/host_debug_unopt_arm64",
+                "targets":
+                [ "flutter/impeller/golden_tests:impeller_golden_tests"]
+            },
+            "properties":
+            {
+                "$flutter/osx_sdk":
+                {
+                    "sdk_version": "15a240d"
+                }
+            }
+        },
         {
             "cas_archive": false,
             "drone_dimensions":

impeller/compiler/BUILD.gn

@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/toolchain/toolchain.gni")
 import("//flutter/impeller/tools/impeller.gni")
 import("//flutter/shell/version/version.gni")
 
@@ -116,3 +117,20 @@ impeller_component("compiler_unittests") {
     "//flutter/testing:testing_lib",
   ]
 }
+
+copy("copy_asan_runtime_dylib") {
+  visibility = [ "*" ]
+
+  if (host_cpu == "arm64") {
+    _libclang_base_path =
+        "$buildtools_path/mac-arm64/clang/lib/clang/18/lib/darwin/"
+  } else {
+    _libclang_base_path =
+        "$buildtools_path/mac-x64/clang/lib/clang/18/lib/darwin/"
+  }
+
+  _dylib_name = "libclang_rt.asan_osx_dynamic.dylib"
+
+  sources = [ "$_libclang_base_path/$_dylib_name" ]
+  outputs = [ "$root_out_dir/$_dylib_name" ]
+}

impeller/tools/shaders.gni

@@ -151,6 +151,11 @@ template("impeller_shaders") {
 
   group(target_name) {
     public_deps = []
+
+    if (is_asan && is_mac) {
+      public_deps += [ "//flutter/impeller/compiler:copy_asan_runtime_dylib" ]
+    }
+
     if (impeller_enable_metal) {
       public_deps += [ ":$mtl_shaders" ]
     }