Fix/improve configs build script (#21086)

buildroot/bin/mftest

@@ -6,7 +6,6 @@
 #  mftest [name] [index] [-y]         Set config options and optionally build a test
 #
 
-MFINFO=$(mfinfo) || exit 1
 [[ -d Marlin/src ]] || { echo "Please 'cd' to the Marlin repo root." ; exit 1 ; }
 
 perror() { echo -e "$0: \033[0;31m$1 -- $2\033[0m" ; }
@@ -37,7 +36,7 @@ env shortcuts: tree due esp lin lpc|lpc8 lpc9 m128 m256|mega stm|f1 f4 f7 s6 tee
 
 TESTPATH=buildroot/tests
 
-STATE_FILE=$( echo ./.pio/.mftestrc )
+STATE_FILE="./.pio/.mftestrc"
 SED=$(which gsed || which sed)
 
 shopt -s extglob nocasematch