Remove -Wa,--noexecstack argument, fix ccache

This option seems really unsupported and breaks the pre-processor
when using ccache:

clang: error: argument unused during compilation:
'-Wa,--noexecstack' [-Werror,-Wunused-command-line-argument]

Removing, given also that this flag is not propagated to the
production build files but used only in standalione builds

Change-Id: I82e6949a96dfb1ea599290699586d6e078adfbe5
diff --git a/gn/standalone/BUILD.gn b/gn/standalone/BUILD.gn
index e88053b..d7fd9b6 100644
--- a/gn/standalone/BUILD.gn
+++ b/gn/standalone/BUILD.gn
@@ -13,8 +13,8 @@
 # limitations under the License.
 
 import("//gn/standalone/android.gni")
-import("//gn/standalone/wasm.gni")
 import("//gn/standalone/sanitizers/sanitizers.gni")
+import("//gn/standalone/wasm.gni")
 
 config("extra_warnings") {
   cflags = [
@@ -79,10 +79,6 @@
     "-Werror",
   ]
 
-  if (!is_wasm && !is_lto) {
-    cflags += [ "-Wa,--noexecstack" ]
-  }
-
   if (is_clang) {
     cflags += [
       # Color compiler output, see https://github.com/ninja-build/ninja/wiki/FAQ