BuildSystem: add cmake variable UEFI_BOOT

If this variable is defined in cmake, image will be build with esp
and booted with uefi.

toolchain/local/grub-legacy-boot.cfg

@@ -0,0 +1,23 @@
+menuentry "banan-os" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2
+}
+
+menuentry "banan-os (no serial)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 noserial
+}
+
+menuentry "banan-os (only serial)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 console=ttyS0
+}
+
+menuentry "banan-os (no apic)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic
+}
+
+menuentry "banan-os (no apic, no serial)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic noserial
+}
+
+menuentry "banan-os (no apic, only serial)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic console=ttyS0
+}

toolchain/local/grub-memdisk.cfg

@@ -0,0 +1,2 @@
+insmod part_gpt
+configfile (hd0,gpt2)/boot/grub/grub.cfg

toolchain/local/grub-uefi.cfg

@@ -0,0 +1,26 @@
+insmod part_gpt
+set root=(hd0,gpt2)
+
+menuentry "banan-os" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2
+}
+
+menuentry "banan-os (no serial)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 noserial
+}
+
+menuentry "banan-os (only serial)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 console=ttyS0
+}
+
+menuentry "banan-os (no apic)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic
+}
+
+menuentry "banan-os (no apic, no serial)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic noserial
+}
+
+menuentry "banan-os (no apic, only serial)" {
+	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic console=ttyS0
+}