[scudo] Fix definition of SCUDO_SMALL_STACK_DEPOT.

[cferris]

Summary

The SCUDO_FUZZ macro is either defined or not defined. The previous
code assumed it had a one or zero value, so change the setting of
SCUDO_SMALL_STACK_DEPOT based on defined(SCUDO_FUZZ).

[ahomescu]

I see what happened: the old code was relying on -DSCUDO_FUZZ setting it to 1, but leaving it undefined defaults it to 0. On a second look, I realized the latter is only true for #if but not macros from #define.

compiler-rt/lib/scudo/standalone/platform.h

 
 #ifndef SCUDO_CAN_USE_MTE
 #define SCUDO_CAN_USE_MTE (SCUDO_LINUX || SCUDO_TRUSTY)
 #endif
 
 // Use smaller table sizes for fuzzing in order to reduce input size.
 // Trusty just has less available memory.
 #ifndef SCUDO_SMALL_STACK_DEPOT
-#define SCUDO_SMALL_STACK_DEPOT (SCUDO_FUZZ || SCUDO_TRUSTY)
+#if defined(SCUDO_FUZZ) || SCUDO_TRUSTY
+#define SCUDO_SMALL_STACK_DEPOT 1
+#else
+#define SCUDO_SMALL_STACK_DEPOT 0
+#endif
 #endif
 
 #ifndef SCUDO_MIN_ALIGNMENT_LOG
 // We force malloc-type functions to be aligned to std::max_align_t, but there
 // is no reason why the minimum alignment for all other functions can't be 8
 // bytes. Except obviously for applications making incorrect assumptions.
 // TODO(kostyak): define SCUDO_MIN_ALIGNMENT_LOG 3
 #define SCUDO_MIN_ALIGNMENT_LOG FIRST_32_SECOND_64(3, 4)