fix terminal encoding for cocoapods

src/objective-c/tests/build_tests.sh

@@ -33,6 +33,9 @@
 
 set -e
 
+# CocoaPods requires the terminal to be using UTF-8 encoding.
+export LANG=en_US.UTF-8
+
 cd $(dirname $0)
 
 hash pod 2>/dev/null || { echo >&2 "Cocoapods needs to be installed."; exit 1; }