[scudo] Make Secondary linker-initialized compliant

[cryptoad]

Summary

As a follow up to D48142 for Scudo, switch the SpinMutex to its static
counterpart, and ensure zero-initialization by memset'ing the whole class.

lib/scudo/scudo_allocator_secondary.h

namespace LargeChunk {
   static Header *getHeader(const void *Ptr) {
     return getHeader(reinterpret_cast<uptr>(Ptr));
   }
 }  // namespace LargeChunk
 
 class ScudoLargeMmapAllocator {
  public:
   void Init() {
-    NumberOfAllocs = 0;
-    NumberOfFrees = 0;
-    AllocatedBytes = 0;
-    FreedBytes = 0;
-    LargestSize = 0;
+    internal_memset(this, 0, sizeof(*this));
   }
 
   void *Allocate(AllocatorStats *Stats, uptr Size, uptr Alignment) {
     const uptr UserSize = Size - Chunk::getHeaderSize();
     // The Scudo frontend prevents us from allocating more than
     // MaxAllowedMallocSize, so integer overflow checks would be superfluous.
     uptr ReservedSize = Size + LargeChunk::getHeaderSize();
     if (UNLIKELY(Alignment > MinAlignment))
Printf("Stats: LargeMmapAllocator: allocated %zd times (%zd K), "
            FreedBytes >> 10, NumberOfAllocs - NumberOfFrees,
            (AllocatedBytes - FreedBytes) >> 10, LargestSize >> 20);
   }
 
  private:
   static constexpr uptr HeadersSize =
       LargeChunk::getHeaderSize() + Chunk::getHeaderSize();
 
-  SpinMutex StatsMutex;
+  StaticSpinMutex StatsMutex;
   u32 NumberOfAllocs;
   u32 NumberOfFrees;
   uptr AllocatedBytes;
   uptr FreedBytes;
   uptr LargestSize;
 };
 
 #endif  // SCUDO_ALLOCATOR_SECONDARY_H_