Add rand.init_as_system to allow for system-level based random number generation

core/math/rand/system_linux.odin

@@ -0,0 +1,27 @@
+package rand
+
+import "core:sys/unix"
+
+_system_random :: proc() -> u32 {
+	for {
+		value: u32
+		ret := unix.sys_getrandom(([^]u8)(&value), 4, 0)
+		if ret < 0 {
+			switch ret {
+			case -4: // EINTR
+				// Call interupted by a signal handler, just retry the request.
+				continue
+			case -38: // ENOSYS
+				// The kernel is apparently prehistoric (< 3.17 circa 2014)
+				// and does not support getrandom.
+				panic("getrandom not available in kernel")
+			case:
+				// All other failures are things that should NEVER happen
+				// unless the kernel interface changes (ie: the Linux
+				// developers break userland).
+				panic("getrandom failed")
+			}
+		}
+		return value
+	}
+}