Remove sysroot and mmacosx-version-min flag for mac/arm builds

Things should build fine without this (the default min version for
arm builds is macOS 11.0, and the default build already passes in
a sysroot), and at least on my system swiftshader builds fine
in an intel->arm cross build without this.

Change-Id: Id408a935f996bdf316d90f150531a4c5855a61f3
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/55628
Tested-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Commit-Queue: Nico Weber <thakis@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 50c16e3..47753c7 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -49,18 +49,6 @@
     cflags = [ "-fno-operator-names" ]
     cflags_cc = [ "-std=c++17" ]
 
-    # On macOS for the ARM architecture, some C++17 features require version
-    # 10.14, while Chrome must support 10.11 (El Capitan). However, the first
-    # 'Apple Silicon' devices launched with macOS 11.0 (Big Sur).
-    # TODO(b/174843857): Remove once Chrome demands macOS 10.14.
-    if (is_mac && current_cpu == "arm64") {
-      cflags += [
-        "-isysroot",
-        rebase_path(sysroot, root_build_dir),
-        "-mmacosx-version-min=10.14.0",
-      ]
-    }
-
     defines +=
         [ "NO_SANITIZE_FUNCTION=__attribute__((no_sanitize(\"function\")))" ]