When building as standalone GC the free object is initialized with 0 …

…flags. This leads to the free list plugs not having the right size on heap traversal (often leading to a crash). The fix is for the free object to be an array with a compenent size of 1 byte.

Commit migrated from dotnet/coreclr@6a1c28f

src/coreclr/src/gc/env/gcenv.object.h

@@ -53,7 +53,7 @@ class MethodTable
     {
         m_baseSize = 3 * sizeof(void *);
         m_componentSize = 1;
-        m_flags = 0;
+        m_flags = MTFlag_HasComponentSize | MTFlag_IsArray;
     }
 
     uint32_t GetBaseSize()