Add UVM32_SYSCALL_RAND to get a "true" random number from the host, as I want to play zigtris and not have it be the same every time.

apps/zigtris/src/main.zig

@@ -10,7 +10,7 @@ export fn main() void {
     var gameRunning = true;
     var lastUpdate:u32 = 0;
 
-    zigtris.gamesetup(console, uvm.millis()) catch |err| {
+    zigtris.gamesetup(console, uvm.rand()) catch |err| {
         _ = console.print("err {any}\n", .{err}) catch 0;
         _ = console.flush() catch 0;
         return;

apps/zigtris/src/uvm.zig

@@ -27,6 +27,10 @@ pub inline fn millis() u32 {
     return syscall(uvm32.UVM32_SYSCALL_MILLIS, 0, 0);
 }
 
+pub inline fn rand() u32 {
+    return syscall(uvm32.UVM32_SYSCALL_RAND, 0, 0);
+}
+
 // dupeZ would be better, but want to avoid using an allocator
 // this is of course, unsafe...
 var termination_buf:[128]u8 = undefined;