libvpx: Pull from upstream

source/libvpx/build/make/configure.sh

Index: source/libvpx/build/make/configure.sh
diff --git a/source/libvpx/build/make/configure.sh b/source/libvpx/build/make/configure.sh
old mode 100755
new mode 100644
index c5bed61bec8a48dd9ff05bcb212c15ac5324f27a..688fa12c52a36357f0baf1c5d5421a9a1b71ac4e
--- a/source/libvpx/build/make/configure.sh
+++ b/source/libvpx/build/make/configure.sh
@@ -728,6 +728,13 @@ process_common_toolchain() {
   # Handle darwin variants. Newer SDKs allow targeting older
   # platforms, so use the newest one available.
   case ${toolchain} in
+    arm*-darwin*)
+      ios_sdk_dir="$(show_darwin_sdk_path iphoneos)"
+      if [ -d "${ios_sdk_dir}" ]; then
+        add_cflags  "-isysroot ${ios_sdk_dir}"
+        add_ldflags "-isysroot ${ios_sdk_dir}"
+      fi
+      ;;
     *-darwin*)
       osx_sdk_dir="$(show_darwin_sdk_path macosx)"
       if [ -d "${osx_sdk_dir}" ]; then
@@ -803,7 +810,14 @@ process_common_toolchain() {
           if disabled neon && enabled neon_asm; then
             die "Disabling neon while keeping neon-asm is not supported"
           fi
-          soft_enable media
+          case ${toolchain} in
+            *-darwin*)
+              # Neon is guaranteed on iOS 6+ devices, while old media extensions
+              # no longer assemble with iOS 9 SDK
+              ;;
+            *)
+              soft_enable media
+          esac
           ;;
         armv6)
           soft_enable media