fix splitting bootloader string

the existing solution simply did not work

scripts/build/binary_hdd

@@ -56,9 +56,7 @@ Check_package chroot /sbin/parted parted
 Check_package host /sbin/fdisk fdisk
 Check_package host /sbin/losetup mount
 
-echo "${LB_BOOTLOADERS}" | \
-while IFS="," read -r BOOTLOADER
-do
+for BOOTLOADER in $(echo "${LB_BOOTLOADERS}" | tr "," "\n"); do
 	case "${BOOTLOADER}" in
 		grub)
 			Check_package chroot /usr/sbin/grub grub

scripts/build/source_debian

@@ -57,9 +57,7 @@ Chroot chroot "sh source-selection.sh"
 rm -f chroot/source-selection.sh
 mv chroot/source-selection.txt ./
 
-echo "${LB_BOOTLOADERS}" | \
-while IFS="," read -r BOOTLOADER
-do
+for BOOTLOADER in $(echo "${LB_BOOTLOADERS}" | tr "," "\n"); do
 	echo "${BOOTLOADER}" >> source-selection.txt
 done