[gn] Port exec_script whitelist from chromium/src/build

BUG=chromium:617873
NOTRY=true
TBR=jochen@chromium.org, vogelheim@chromium.org

Review-Url: https://codereview.chromium.org/2046563004
Cr-Commit-Position: refs/heads/master@{#36773}

.gn

@@ -29,14 +29,22 @@ exec_script_whitelist = [
   "//build/config/compiler/BUILD.gn",
   "//build/config/gcc/gcc_version.gni",
   "//build/config/ios/ios_sdk.gni",
+  "//build/config/linux/atk/BUILD.gn",
   "//build/config/linux/BUILD.gn",
   "//build/config/linux/pkg_config.gni",
   "//build/config/mac/mac_sdk.gni",
   "//build/config/posix/BUILD.gn",
   "//build/config/sysroot.gni",
+  "//build/config/win/BUILD.gn",
   "//build/config/win/visual_studio_version.gni",
+  "//build/gn_helpers.py",
+  "//build/gypi_to_gn.py",
+  "//build/toolchain/concurrent_links.gni",
   "//build/toolchain/gcc_toolchain.gni",
   "//build/toolchain/mac/BUILD.gn",
+  "//build/toolchain/nacl/BUILD.gn",
   "//build/toolchain/win/BUILD.gn",
+  "//build/util/branding.gni",
+  "//build/util/version.gni",
   "//test/test262/BUILD.gn",
 ]