bootloader: align during docker build

bootloader-docker-build.sh

@@ -12,7 +12,7 @@ docker run -t -v $(pwd)/output:/output $IMAGETAG /bin/sh -c "\
 	git submodule update --init && \
 	CFLAGS='-std=c99' make -C vendor/libopencm3 && \
 	make && \
-	make -C bootloader && \
+	make -C bootloader align && \
 	cp bootloader/bootloader.bin /output/bootloader-$FIRMWARETAG.bin"
 
 echo "---------------------"

bootloader/firmware_align.py

@@ -7,5 +7,5 @@ fs = os.stat(fn).st_size
 if fs > 32768:
 	raise Exception('bootloader has to be smaller than 32768 bytes')
 with open(fn, 'ab') as f:
-	f.write(os.urandom(32768 - fs))
+	f.write(b'\xFF' * (32768 - fs))
 	f.close()