BuildSystem: Move all userpace libraries under the userspace directory

As the number of libraries is increasing, root directory starts to
expand. This adds better organization for libraries

userspace/libraries/LibC/arch/x86_64/crt0.S

@@ -0,0 +1,35 @@
+.section .text
+
+.global _start
+_start:
+	pushq $0
+	pushq %rdi
+	pushq %rsi
+	pushq %rdx
+
+	# STACK LAYOUT
+	#   null
+	#   argc
+	#   argv
+	#   envp
+
+	xorq %rbp, %rbp
+
+	# init libc
+	movq 0(%rsp), %rdi
+	call _init_libc
+
+	# call global constructors
+	call _init
+
+	# call main
+	movq 16(%rsp), %rdi
+	movq  8(%rsp), %rsi
+	movq  0(%rsp), %rdx
+	call main
+
+	# call exit
+	movq %rax, %rdi
+	call exit
+
+.size _start, . - _start