change ubuntu to archlinux to fix CI problem

.gitlab-ci.yml

-image: ubuntu
+image: archlinux/base
 
 before_script:
-    - apt update
-    - apt install -y nasm g++ make
+    - pacman -Sy
+    - pacman -S --noconfirm nasm gcc make
 
 build32:
     script:

kernel/Makefile

@@ -10,10 +10,6 @@ endif
 
 assemble: kernel head
 	ld -o kernel.img -Ttext 0x7e00 --oformat binary image_head.o kernel.o -m elf_$(ARCH)
-	# Sector 1 = bootloader, Sector 2 - (512B TO 64K) = kernel
-	# Extend kernel.img to correct size. 
-	test $$(stat -c %s kernel.img) -le 65024
-	truncate --size=65024 kernel.img
 
 head:
 	nasm -f elf$(BITS) -DTARGET_BITS=$(BITS) image_head.asm -o image_head.o