Adjust the stack pointer before calling the C code to account for the current stack frame.
// Call the 'C' handler with the current stack pointer
// as argument, e.g.:
// go_write(stackptr)
- mov %rsp, 0x08(%rsp)
+ mov %rsp, %r11
+ add $0x20, %r11
+ mov %r11, 0x08(%rsp)
lea \c_func@GOTPCREL(%rip), %r11
mov (%r11), %r11
mov %r11, (%rsp)
