simplify initialising variables in shell scripts

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/build/boot/roms_helper

@@ -14,41 +14,21 @@ set -u -e
 
 read projectname < projectname
 
+seavgabiosrom="elf/seabios/default/libgfxinit/vgabios.bin"
+grub_background="background1280x800.png"
+grubelf="elf/grub/grub.elf"
 cfgsdir="config/coreboot"
-
-blobs_required=""
-
-ubdir=""
 kmapdir="config/grub/keymap"
 
-grub_timeout=""
-grub_scan_disk="undefined"
-tree="undefined"
-arch="undefined"
-
 # Disable all payloads by default.
 # target.cfg files have to specifically enable [a] payload(s)
-payload_grub="n"
-payload_grub_withseabios="n" # seabios chainloaded from grub
-payload_seabios="n"
-payload_seabios_withgrub="n" # i386-coreboot grub from SeaBIOS boot menu
-payload_memtest="n"
-payload_uboot="n"
-uboot_config="undefined"
+eval "$(setvars "n" payload_grub payload_grub_withseabios payload_seabios \
+    payload_seabios_withgrub payload_memtest payload_uboot)"
 
-romdir=""
-cbdir=""
-cbfstool=""
-corebootrom=""
-seavgabiosrom="elf/seabios/default/libgfxinit/vgabios.bin"
-grub_background="background1280x800.png"
+eval "$(setvars "" romdir cbdir cbfstool corebootrom initmode displaymode \
+    cbcfg targetdir grub_timeout ubdir blobs_required)"
 
-initmode=""
-displaymode=""
-cbcfg=""
-targetdir=""
-
-grubelf="elf/grub/grub.elf"
+eval "$(setvars "undefined" grub_scan_disk tree arch uboot_config)"
 
 # main() is in include/boot.sh
 
@@ -120,13 +100,9 @@ configure_target()
 	# Override all payload directives with cmdline args
 	if [ ! -z ${_payload} ]; then
 		printf "setting payload to: %s\n" "${_payload}"
-		payload_grub="n"
-		payload_grub_withseabios="n" # seabios chainloaded from grub
-		payload_seabios="n"
-		payload_seabios_withgrub="n" # i386-coreboot grub from SeaBIOS
-		payload_uboot="n"
-		payload_memtest="n"
-
+		eval "$(setvars "n" payload_grub payload_grub_withseabios \
+		    payload_seabios payload_seabios_withgrub payload_uboot \
+		    payload_memtest)"
 		eval "payload_${_payload}=y"
 	fi
 }
@@ -494,10 +470,8 @@ moverom() {
 
 	[ -d "${newrompath%/*}" ] || mkdir -p "${newrompath%/*}/" || \
 	    err "moverom: cannot create rom directory: \"${newrompath%/*}\""
-
 	[ "${blobs_required}" = "n" ] && \
 		newrompath="${newrompath%.rom}_noblobs.rom"
-
 	cp "${rompath}" "${newrompath}" || err "moverom: can't copy rom"
 }