Update buildenv.sh to detect aarch64 as ARM

Update buildenv.sh to detect aarch64 as on Nvidias Jetson TX1 as ARM architecture. Final goal is to build tensorflow on jetson tx1

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Reviewed-on: https://github.com/bazelbuild/bazel/pull/814
MOS_MIGRATED_REVID=112967980
diff --git a/scripts/bootstrap/buildenv.sh b/scripts/bootstrap/buildenv.sh
index 57c86ba..c2b30fa 100755
--- a/scripts/bootstrap/buildenv.sh
+++ b/scripts/bootstrap/buildenv.sh
@@ -32,7 +32,7 @@
 fi
 
 MACHINE_IS_ARM='no'
-if [ "${MACHINE_TYPE}" = 'arm' -o "${MACHINE_TYPE}" = 'armv7l' ]; then
+if [ "${MACHINE_TYPE}" = 'arm' -o "${MACHINE_TYPE}" = 'armv7l' -o "${MACHINE_TYPE}" = 'aarch64' ]; then
   MACHINE_IS_ARM='yes'
 fi