Failed to take over all threads after multiple attempts.

Hi all
Thanks to release this useful lib for check dynamic memory
when i tride compile with mingw32(msys2) and use dr.memory to debug

> ./drmemory.exe /d/static_test/G_memory_test/build/G_memory_test.exe

i got this error
`~~Dr.M~~ Dr. Memory version 2.4.0
~~Dr.M~~ Running "D:/static_test/G_memory_test/build/G_memory_test.exe"
~~Dr.M~~ Using system call file C:\Users\KARTHY\AppData\Roaming\Dr. Memory\symcache\syscalls_wow64.txt

~~Dr.M~~ WARNING: application exited with abnormal code 0x28`

this is my CMakeFile and source file, thanks a lot!

`cmake_minimum_required(VERSION 3.5)

project(G_memory_test)

add_definitions(-ggdb)
add_definitions(-static-libgcc)
add_definitions(-static-libstdc++)

add_executable(${PROJECT_NAME}
${PROJECT_SOURCE_DIR}/main.cpp
)`

`#include

void test1();
void test2();
void test3();
void test4();

int main()
{
test4();
std::cout << "ok" << std::endl;
return 0;
}

void test1()
{
char *ptr;
for (int i = 0; i<100; i++) {
ptr = (char*)malloc(i);
if (i % 2){free(ptr)};
}
}

void test2()
{
char *x = (char*)malloc(8);
char c = *(x + 8); // buffer overlow
free(x);
c = *x; // read free memory
}

typedef struct T_ {
char a;
char b;
}T;

void test3()
{
T a, b;
char x;
a.a = 'a';
a.b = 'b';
b.a = x;
if (b.a == 10)
memcpy(&b, &a, sizeof(T));
}

void test4()
{
char * ptr = NULL;
ptr = new char;
free(ptr);
free(ptr);
}`