clock_getres: don't assume time_t is 32-bit on 32-bit archs

the time64 syscall for this is not necessary or useful, since clock
resolution is generally better than 68-year granularity. if there's a
32-bit syscall, use it and expand the result into timespec; otherwise
there is only one syscall and it does the right thing to store to
timespec directly.

on 64-bit archs, there is no change to the code after preprocessing.

src/time/clock_getres.c

@@ -3,5 +3,19 @@
 
 int clock_getres(clockid_t clk, struct timespec *ts)
 {
+#ifdef SYS_clock_getres_time64
+	/* On a 32-bit arch, use the old syscall if it exists. */
+	if (SYS_clock_getres != SYS_clock_getres_time64) {
+		long ts32[2];
+		int r = __syscall(SYS_clock_getres, clk, ts32);
+		if (!r) {
+			ts->tv_sec = ts32[0];
+			ts->tv_nsec = ts32[1];
+		}
+		return __syscall_ret(r);
+	}
+#endif
+	/* If reaching this point, it's a 64-bit arch or time64-only
+	 * 32-bit arch and we can get result directly into timespec. */
 	return syscall(SYS_clock_getres, clk, ts);
 }