pthread fails to link without a call in main - c++

Question

I've been attempting to use angelscript and I keep getting linker errors, however if I put a reference to pthread_exit(NULL) at the end of my main function it builds, links, and runs normally.
Here is the code in question:
#include <iostream>
#include <angelscript.h>
#include <cassert>
// This is used for AngelScript error messages
void MessageCallback(const asSMessageInfo &msg)
{
const char *type = "ERR ";
if( msg.type == asMSGTYPE_WARNING )
{
type = "WARN";
}
else if( msg.type == asMSGTYPE_INFORMATION )
{
type = "INFO";
}
std::cout << msg.section << " (" << msg.row << ", " << msg.col << ") : " << type << " : " << msg.message << std::endl;
}
int main(void)
{
asIScriptEngine* engine = asCreateScriptEngine(ANGELSCRIPT_VERSION);
int r = engine->SetMessageCallback(asFUNCTION(MessageCallback), 0, asCALL_CDECL);
assert(r >= 0);
std::cout << "Testing" << std::endl;
engine->Release();
pthread_exit(NULL);
return 0;
}
and this is the command line:
g++ -Wl,-O1,--sort-common,--as-needed,-z,relro -Wl,-O1 -o fib main.o -langelscript -lpthread
any ideas?