Adds justfile to build everything

user/test_pic/src/main.rs

@@ -0,0 +1,21 @@
+#![no_std]
+#![no_main]
+
+#[panic_handler]
+fn panic(_panic_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn entry() {
+    let test = "Hello from user mode";
+    unsafe {
+        core::arch::asm!(
+            "ecall",
+            in("a0") 999,
+            in("a1") test.as_ptr(),
+            in("a2") test.len(),
+            clobber_abi("system")
+        );
+    }
+}