Use the system getenv in setup_debug_log

As ruby_set_debug_option() is called before ruby_sysinit(),
CRITICAL_SECTIONs are not initialized yet.

debug.c

@@ -263,6 +263,7 @@ ruby_set_debug_option(const char *str)
 }
 
 #if RUBY_DEVEL
+#undef getenv
 
 // RUBY_DEBUG_LOG features
 // See vm_debug.h comments for details.

win32/win32.c

@@ -811,7 +811,6 @@ StartSockets(void)
     InitializeCriticalSection(&select_mutex);
     InitializeCriticalSection(&socklist_mutex);
     InitializeCriticalSection(&conlist_mutex);
-    InitializeCriticalSection(&uenvarea_mutex);
 
     atexit(exit_handler);
 }
@@ -896,6 +895,7 @@ rb_w32_sysinit(int *argc, char ***argv)
 #endif
     SetErrorMode(SEM_FAILCRITICALERRORS|SEM_NOGPFAULTERRORBOX);
 
+    InitializeCriticalSection(&uenvarea_mutex);
     get_version();
 
     //