Fix unset-insert-libraries-on-exec.cc to use "%env" to make it work in iOS simulator.
// execl().
// RUN: %run %t %T/echo-env >/dev/null 2>&1
-// RUN: env DYLD_INSERT_LIBRARIES=%t-darwin-dummy-shared-lib-so.dylib \
+// RUN: %env DYLD_INSERT_LIBRARIES=%t-darwin-dummy-shared-lib-so.dylib \
// RUN: %run %t %T/echo-env 2>&1 | FileCheck %s || exit 1
#if !defined(SHARED_LIB)
