raspberrypi-bootloader: support Raspberry Pi 3 w/o U-Boot and explicitly support

Raspberry Pi Zero

nixos/modules/system/boot/loader/raspberrypi/uboot-builder.sh

@@ -0,0 +1,29 @@
+#! @bash@/bin/sh -e
+
+copyForced() {
+    local src="$1"
+    local dst="$2"
+    cp $src $dst.tmp
+    mv $dst.tmp $dst
+}
+
+# Call the extlinux builder
+"@extlinuxConfBuilder@" "$@"
+
+# Add the firmware files
+fwdir=@firmware@/share/raspberrypi/boot/
+copyForced $fwdir/bootcode.bin  /boot/bootcode.bin
+copyForced $fwdir/fixup.dat     /boot/fixup.dat
+copyForced $fwdir/fixup_cd.dat  /boot/fixup_cd.dat
+copyForced $fwdir/fixup_db.dat  /boot/fixup_db.dat
+copyForced $fwdir/fixup_x.dat   /boot/fixup_x.dat
+copyForced $fwdir/start.elf     /boot/start.elf
+copyForced $fwdir/start_cd.elf  /boot/start_cd.elf
+copyForced $fwdir/start_db.elf  /boot/start_db.elf
+copyForced $fwdir/start_x.elf   /boot/start_x.elf
+
+# Add the uboot file
+copyForced @uboot@/u-boot.bin /boot/u-boot-rpi.bin
+
+# Add the config.txt
+copyForced @configTxt@ /boot/config.txt