Use Rust for formatting

The fprintf implementation included in crt0 is too rudimental

native/src/init/rootdir.rs

@@ -0,0 +1,37 @@
+use std::fs::File;
+use std::io::Write;
+use std::mem;
+use std::os::fd::{FromRawFd, RawFd};
+
+use base::{debug, Utf8CStr};
+
+pub fn inject_magisk_rc(fd: RawFd, tmp_dir: &Utf8CStr) {
+    debug!("Injecting magisk rc");
+
+    let mut file = unsafe { File::from_raw_fd(fd) };
+
+    write!(
+        file,
+        r#"
+on post-fs-data
+    start logd
+    exec {1} 0 0 -- {0}/magisk --post-fs-data
+
+on property:vold.decrypt=trigger_restart_framework
+    exec {1} 0 0 -- {0}/magisk --service
+
+on nonencrypted
+    exec {1} 0 0 -- {0}/magisk --service
+
+on property:sys.boot_completed=1
+    exec {1} 0 0 -- {0}/magisk --boot-complete
+
+on property:init.svc.zygote=stopped
+    exec {1} 0 0 -- {0}/magisk --zygote-restart
+"#,
+        tmp_dir, "u:r:magisk:s0"
+    )
+    .ok();
+
+    mem::forget(file)
+}