[HWASAN][LSAN] Replace cstdint with stdint.h

[MaskRay]

Technically stdint.h is slightly better since we use uintptr_t instead of std::uintptr_t, though in practice the two headers can be mixed...

compiler-rt/test/lsan/TestCases/user_pointer.cpp

 // Checks if a user pointer is found by the leak sanitizer.
 // RUN: %clang_lsan %s -o %t
 // RUN: %run %t 2>&1
 
-#include <cstdint>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 
 uintptr_t glob[1024];
 
 int main() {
   for (int i = 0; i < 1024; ++i) {
     // Check that the pointers will not be falsely reported as leaks.
     glob[i] = (uintptr_t)malloc(sizeof(int *));
   }
   return 0;
 }