BuildSystem: cmake can now build out libc

I can't seem to get libc++ build to work...

kernel/arch/x86_64/crt0.S

@@ -0,0 +1,31 @@
+.section .text
+
+.global _start
+_start:
+	# Set up end of the stack frame linked list.
+	movq $0, %rbp
+	pushq %rbp # rip=0
+	pushq %rbp # rbp=0
+	movq %rsp, %rbp
+
+	# We need those in a moment when we call main.
+	pushq %rsi
+	pushq %rdi
+
+	# Prepare signals, memory allocation, stdio and such.
+	call initialize_standard_library
+
+	# Run the global constructors.
+	call _init
+
+	# Restore argc and argv.
+	popq %rdi
+	popq %rsi
+
+	# Run main
+	call main
+
+	# Terminate the process with the exit code.
+	movl %eax, %edi
+	call exit
+.size _start, . - _start