Add magiskboot to kernelsu working directory (#1684)

Add the magiskboot binary to the /data/adb/ksu/bin directory so that
scripts/programs can call magiskboot to patch the boot/init_boot image.

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Co-authored-by: weishu <twsxtd@gmail.com>

userspace/ksud/src/defs.rs

@@ -12,6 +12,7 @@ pub const PROFILE_TEMPLATE_DIR: &str = concatcp!(PROFILE_DIR, "templates/");
 pub const KSURC_PATH: &str = concatcp!(WORKING_DIR, ".ksurc");
 pub const KSU_OVERLAY_SOURCE: &str = "KSU";
 pub const DAEMON_PATH: &str = concatcp!(ADB_DIR, "ksud");
+pub const MAGISKBOOT_PATH: &str = concatcp!(BINARY_DIR, "magiskboot");
 
 #[cfg(target_os = "android")]
 pub const DAEMON_LINK_PATH: &str = concatcp!(BINARY_DIR, "ksud");