go runtime fails to compile - go

Question

I am just wondering why would go runtime fail to build. How do we pass flags (-fpermissive in this case) to the c compiler which golang compiler is using to build the runtime. I am using gcc-4.6.2 on ubuntu 12.04
../../../thirdparty/go1.4.2/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/src/runtime/cgo/gcc_linux_amd64.c: In function ‘void _cgo_sys_thread_start(ThreadStart*)’:
../../../thirdparty/go1.4.2/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/src/runtime/cgo/gcc_linux_amd64.c:45:41: error: invalid conversion from ‘void*’ to ‘__sigset_t*’ [-fpermissive]
A sample program written also fails to compile, it seems the nil defined in the go code is the problem, i wonder how others are working, when does the golang compiler compiles this runtime code ?
gcc t.c -lpthread -o t
t.c: In function ‘void* hello_world(void*)’:
t.c:12:41: error: invalid conversion from ‘void*’ to ‘__sigset_t*’ [-fpermissive]
/usr/include/x86_64-linux-gnu/bits/sigthread.h:31:12: error: initializing argument 3 of ‘int pthread_sigmask(int, const __sigset_t*, __sigset_t*)’ [-fpermissive]
rk#rk-VirtualBox:~$ gcc -fpermissive t.c -lpthread -o t
t.c: In function ‘void* hello_world(void*)’:
t.c:12:41: warning: invalid conversion from ‘void*’ to ‘__sigset_t*’ [-fpermissive]
rk#rk-VirtualBox:~$ cat t.c
#include<pthread.h>
#include<stdio.h>
#include<signal.h>
#define nil ((void*)0)
static void*
hello_world(void *vptr)
{
sigset_t set;
sigemptyset(&set);
pthread_sigmask(SIG_BLOCK, &set, nil);
printf("hello world");
return NULL;
}
int main(int ac, char **av)
{
pthread_t t;
pthread_create(&t, NULL, hello_world, NULL);
pthread_join(t, NULL);
return 0;
}
/usr/include/x86_64-linux-gnu/bits/sigthread.h:31:12: error: initializing argument 3 of ‘int pthread_sigmask(int, const __sigset_t*, __sigset_t*)’ [-fpermissive]
make: *** [rulemanager] Error 2