Move use_system_xcode to //build_overrides/build.gni

build/toolchain/toolchain.gni

Index: build/toolchain/toolchain.gni
diff --git a/build/toolchain/toolchain.gni b/build/toolchain/toolchain.gni
index 4e49678ab920a3f69e03899038b947a3ef62526b..baa4387d151cd523719fa945e0e09f167f633a61 100644
--- a/build/toolchain/toolchain.gni
+++ b/build/toolchain/toolchain.gni
@@ -5,6 +5,7 @@
 # Toolchain-related configuration that may be needed outside the context of the
 # toolchain() rules themselves.
 
+import("//build_overrides/build.gni")
 import("//build/config/chrome_build.gni")
 
 declare_args() {
@@ -40,24 +41,6 @@ declare_args() {
   # with the build. Used on iOS to ship official builds (as they are built
   # with the version of clang shipped with Xcode).
   use_xcode_clang = is_ios && is_official_build
-
-  # Use the system install of Xcode for tools like ibtool, libtool, etc.
-  # This does not affect the compiler. When this variable is false, targets will
-  # instead use a hermetic install of Xcode. [The hermetic install can be
-  # obtained with gclient sync after setting the environment variable
-  # FORCE_MAC_TOOLCHAIN].
-  use_system_xcode = ""
-}
-
-if (use_system_xcode == "") {
-  if (target_os == "mac") {
-    _result =
-        exec_script("//build/mac/should_use_hermetic_xcode.py", [], "value")
-    use_system_xcode = _result == 0
-  }
-  if (target_os == "ios") {
-    use_system_xcode = true
-  }
 }
 
 # The path to the hermetic install of Xcode. Only relevant when