Make aarch64 compilable

Architecture/aarch64/Bootstrap/boot.S

@@ -0,0 +1,36 @@
+/* Based on this tutorial:
+   https://github.com/s-matyukevich/raspberry-pi-os */
+
+.section ".text.boot"
+
+.extern _bss_start
+.extern _bss_end
+
+.extern arm64Entry
+memzero:
+    str xzr, [x0], #8
+    subs x1, x1, #8
+    b.gt memzero
+    ret
+
+.global _start
+_start:
+    mrs x0, mpidr_el1
+    and x0, x0, #0xFF
+    cbz x0, _start2
+    b CPU_Loop
+
+_start2:
+    adr x0, _bss_start
+    adr x1, _bss_end
+    sub x1, x1, x0
+    bl memzero
+    mov sp, #0x200000
+    bl arm64Entry
+
+Halt:
+    wfe
+    b Halt
+
+CPU_Loop:
+    b CPU_Loop