xbmk: reintroduce setvar as newvar (init only)

use the simpler logic recently introduced, generalised
but it only sets variables to empty. this is safer than
the previous design, and brings the same reduction in
sloccount overall since i wasn't doing anything other
than emptying variables anyway, when it was used before.

i didn't like the long list of variables inside files,
so this makes everything more readable.

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

include/inject.sh

@@ -4,16 +4,6 @@
 # Copyright (c) 2022 Ferass El Hafidi <vitali64pmemail@protonmail.com>
 # Copyright (c) 2023-2026 Leah Rowe <leah@libreboot.org>
 
-archive=""
-board=""
-boarddir=""
-IFD_platform=""
-ifdprefix=""
-new_mac=""
-tmpromdir=""
-tree=""
-xchanged=""
-
 cbcfgsdir="config/coreboot"
 tmpromdel="$XBMK_CACHE/DO_NOT_FLASH"
 nvmutil="util/nvmutil/nvmutil"
@@ -21,8 +11,8 @@ ifdtool="elf/coreboot/default/ifdtool"
 
 checkvars="CONFIG_GBE_BIN_PATH ${checkvarsxbmk-} ${checkvarschk-}"
 
-eval "`printf "%s\n" "$checkvars" | \
-    awk '{ for (i=1; i<=NF; i++) $i = $i "=;"; print }'`"
+eval "`newvar archive board boarddir IFD_platform ifdprefix \
+    new_mac tmpromdir tree xchanged $checkvars`"
 
 inject()
 {