Fix gyp_v8 to work with use_system_icu=1

build/gyp_v8

Index: build/gyp_v8
diff --git a/build/gyp_v8 b/build/gyp_v8
index 73a66a72fd5c0736c399a255aa2d1be281c13373..92e6503925cda4c72245821bff6061c9dd593429 100755
--- a/build/gyp_v8
+++ b/build/gyp_v8
@@ -47,6 +47,10 @@ if __name__ == '__main__':
 sys.path.insert(0, os.path.join(v8_root, 'build', 'gyp', 'pylib'))
 import gyp
 
+# Add paths so that pymod_do_main(...) can import files.
+sys.path.insert(
+    1, os.path.abspath(os.path.join(v8_root, 'tools', 'generate_shim_headers')))
+
 
 def apply_gyp_environment(file_path=None):
   """