[UBSan] Fix test cast-overflow.cc for mips64 big-endian.

[slthakur]

Summary

Gcc for mips does not define BIG_ENDIAN. This causes getFloatValue to return the value of data from 32-bit LSB instead of MSB. Using macro __MIPSEB which is defined by gcc fixes the test cast_overflow.cc.

[samsonov]

This was fixed recently, please update.

[slthakur]

Test passes with the recent fix. Thanks!

lib/ubsan/ubsan_value.cc

#if 0
       case 16: {
         __fp16 Value;
         internal_memcpy(&Value, &Val, 4);
         return Value;
       }
 #endif
       case 32: {
         float Value;
-#if defined(__BIG_ENDIAN__)
+#if defined(__BIG_ENDIAN__) || defined(__MIPSEB)
        // For big endian the float value is in the last 4 bytes.
        // On some targets we may only have 4 bytes so we count backwards from
        // the end of Val to account for both the 32-bit and 64-bit cases.
        internal_memcpy(&Value, ((const char*)(&Val + 1)) - 4, 4);
 #else 
        internal_memcpy(&Value, &Val, 4);
 #endif
         return Value;