Change default arch for banchan to arm64

Devices that only support 32-bit are very uncommon. Default
to the arch that module authors are most likely to be using.

Test: banchan com.android.sdkext | grep TARGET_PRODUCT
Test: banchan com.android.sdkext arm | grep TARGET_PRODUCT
Test: banchan com.android.sdkext arm64 | grep TARGET_PRODUCT
Change-Id: I31734660318eabbe3279214980b5cdecb55ab80b
(cherry picked from commit 0328e326210604fd8e684d0fb5d354f5a34eaf3a)
Merged-In: I31734660318eabbe3279214980b5cdecb55ab80b
diff --git a/envsetup.sh b/envsetup.sh
index be6061d..d08028c 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -890,7 +890,7 @@
     fi
 
     if [ -z "$product" ]; then
-        product=arm
+        product=arm64
     elif [ $(echo $product | wc -w) -gt 1 ]; then
         echo "banchan: Error: Multiple build archs or products supplied: $products"
         return