run-test262 required pthreads, so let's add that. In addition, in MinGW,
clock_gettime is implemented in the pthreads library, so we want to link
it too.
This doesn't get us anywhere closer to building with ClangCL on Windows,
but hey, another target that required some tweaking...
~~~
/home/runner/work/quickjs/quickjs/qjs.c:506:28: error: ‘best[3]’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
506 | if (i == 0 || best[j] > ms)
| ~~~~~~~^~~~~~~~~~~~~~~
/home/runner/work/quickjs/quickjs/qjs.c:506:28: error: ‘best[2]’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
/home/runner/work/quickjs/quickjs/qjs.c:506:28: error: ‘best[1]’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
~~~
