[esan] Fix uninitialized warning from interception context

The interception context is not used by esan, but the compiler complains
about it being uninitialized all the same.  We set it to null to avoid the
warning.

llvm-svn: 267376

compiler-rt/lib/esan/esan_interceptors.cpp

@@ -44,11 +44,13 @@ using namespace __esan; // NOLINT
 
 #define COMMON_INTERCEPT_FUNCTION(name) INTERCEPT_FUNCTION(name)
 
+// We currently do not use ctx.
 #define COMMON_INTERCEPTOR_ENTER(ctx, func, ...)                               \
   do {                                                                         \
     if (UNLIKELY(COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)) {                 \
       return REAL(func)(__VA_ARGS__);                                          \
     }                                                                          \
+    ctx = nullptr;                                                             \
     (void)ctx;                                                                 \
   } while (false)