Started executing vulkan unit tests with validation on macos (flutter/engine#42337)

fixes https://github.com/flutter/flutter/issues/127634

This PR depends on a buildroot change at https://github.com/flutter/buildroot/pull/737

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

DEPS

@@ -256,7 +256,7 @@ allowed_hosts = [
 ]
 
 deps = {
-  'src': 'https://github.com/flutter/buildroot.git' + '@' + 'e522d38d629d7522f0589e754886ed2b82232d9e',
+  'src': 'https://github.com/flutter/buildroot.git' + '@' + '859e7ccc38f55f89dac8aea49367b7a4c1656490',
 
    # Fuchsia compatibility
    #

engine/src/flutter/impeller/BUILD.gn

@@ -103,7 +103,12 @@ impeller_component("impeller_unittests") {
   }
 
   if (glfw_vulkan_library != "") {
-    deps += [ "//third_party/swiftshader" ]
+    deps += [
+      "//third_party/swiftshader",
+      "//third_party/vulkan-deps/vulkan-loader/src:libvulkan",
+      "//third_party/vulkan_validation_layers",
+      "//third_party/vulkan_validation_layers:vulkan_gen_json_files",
+    ]
   }
 
   if (impeller_enable_compute) {

engine/src/flutter/testing/run_tests.py

@@ -75,19 +75,23 @@ def run_cmd(
   print(f'Running command "{command_string}"')
 
   start_time = time.time()
-  collect_output = forbidden_output or allowed_failure_output
-  stdout_pipe = sys.stdout if not collect_output else subprocess.PIPE
-  stderr_pipe = sys.stderr if not collect_output else subprocess.PIPE
 
   process = subprocess.Popen(
       cmd,
-      stdout=stdout_pipe,
-      stderr=stderr_pipe,
+      stdout=subprocess.PIPE,
+      stderr=subprocess.STDOUT,
       env=env,
       universal_newlines=True,
       **kwargs
   )
-  stdout, stderr = process.communicate()
+  output = ''
+
+  for line in iter(process.stdout.readline, ''):
+    output += line
+    sys.stdout.write(line)
+
+  sys.stdout.flush()
+  process.wait()
   end_time = time.time()
 
   if process.returncode != 0 and not expect_failure:
@@ -97,18 +101,11 @@ def run_cmd(
         f'Failed Command:\n\n{command_string}\n\nExit Code: {process.returncode}\n'
     )
 
-    if stdout:
-      print(f'STDOUT: \n{stdout}')
-
-    if stderr:
-      print(f'STDERR: \n{stderr}')
-
     print_divider('!')
 
     allowed_failure = False
     for allowed_string in allowed_failure_output:
-      if (stdout and allowed_string in stdout) or (stderr and
-                                                   allowed_string in stderr):
+      if allowed_string in output:
         allowed_failure = True
 
     if not allowed_failure:
@@ -116,13 +113,8 @@ def run_cmd(
           f'Command "{command_string}" exited with code {process.returncode}.'
       )
 
-  if stdout or stderr:
-    print(stdout)
-    print(stderr)
-
   for forbidden_string in forbidden_output:
-    if (stdout and forbidden_string in stdout) or (stderr and
-                                                   forbidden_string in stderr):
+    if forbidden_string in output:
       raise RuntimeError(
           f'command "{command_string}" contained forbidden string {forbidden_string}'
       )
@@ -489,7 +481,12 @@ def run_cc_tests(build_dir, executable_filter, coverage, capture_core_dump):
             '1',  # Validates accesses to threadgroup memory.
         'MTL_SHADER_VALIDATION_TEXTURE_USAGE':
             '1',  # Validates that texture references are not nil.
+        # Note: built from //third_party/swiftshader
         'VK_ICD_FILENAMES': os.path.join(build_dir, 'vk_swiftshader_icd.json'),
+        # Note: built from //third_party/vulkan_validation_layers:vulkan_gen_json_files
+        # and //third_party/vulkan_validation_layers.
+        'VK_LAYER_PATH': os.path.join(build_dir, 'vulkan-data'),
+        'VK_INSTANCE_LAYERS': 'VK_LAYER_KHRONOS_validation',
     }
     if is_aarm64():
       extra_env.update({
@@ -501,7 +498,7 @@ def run_cc_tests(build_dir, executable_filter, coverage, capture_core_dump):
         build_dir,
         'impeller_unittests',
         executable_filter,
-        shuffle_flags,
+        shuffle_flags + ['--enable_vulkan_validation'],
         coverage=coverage,
         extra_env=extra_env,
         # TODO(117122): Remove this allowlist.

engine/src/flutter/tools/gn

@@ -594,7 +594,8 @@ def to_gn_args(args):
       gn_args['impeller_malioc_path'] = malioc_path
 
   if args.use_glfw_swiftshader:
-    gn_args['glfw_vulkan_library'] = r'\"libvk_swiftshader.dylib\"'
+    if get_host_os() == 'mac':
+      gn_args['glfw_vulkan_library'] = r'\"libvulkan.dylib\"'
 
   # ANGLE is exclusively used for:
   #  - Windows at runtime