xbmk: stricter handling of files on while loops

i overlooked these!

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

include/lib.sh

@@ -106,9 +106,9 @@ fx_()
 
 dx_()
 {
-	[ -f "$2" ] && while read -r fx; do
+	[ ! -f "$2" ] || while read -r fx; do
 		$1 "$fx" || return 1
-	done < "$2"; :
+	done < "$2" || err "dx_ $*: cannot read '$2'"; :
 }
 
 x_()

include/tree.sh

@@ -332,8 +332,9 @@ check_makefile()
 
 copy_elf()
 {
-	[ -f "$listfile" ] && x_ mkdir -p "$dest_dir" && while read -r f; do
+	[ -f "$listfile" ] && x_ mkdir -p "$dest_dir"
+	[ ! -f "$listfile" ] || while read -r f; do
 		[ -f "$srcdir/$f" ] && x_ cp "$srcdir/$f" "$dest_dir"
-	done < "$listfile"
+	done < "$listfile" || err "copy_elf $*: cannot read '$listfile'"
 	x_ make clean -C "$srcdir" $cleanargs
 }