mk: Allow use of x_ on prefix functions

Use this for the sha512sum command, on the main mk
script at the function check_project_hashes().

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

include/lib.sh

@@ -146,7 +146,7 @@ find_ex()
 	$errx find "$@" 2>/dev/null | sort > "$fd" || \
 	    $err "!find $(echo "$@") > \"$fd\""
 	while read -r fx; do
-		"$xx" "$fx" || break; :
+		$xx "$fx" || break; :
 	done < "$fd"
 	x_ rm -f "$fd"
 }

mk

@@ -277,7 +277,7 @@ check_project_hashes()
 	[ ! -f "$XBMK_CACHE/hash/$project$tree" ] || \
 	    read -r old_pjhash < "$XBMK_CACHE/hash/$project$tree"
 
-	fx_ sha512sum "$datadir" "$configdir/$tree" "$mdir" \
+	fx_ "x_ sha512sum" "$datadir" "$configdir/$tree" "$mdir" \
 	    -type f -not -path "*/.git*/*" | awk '{print $1}' > \
 	    "$xbmktmp/project.hash" || $err "!h $project $tree"