lbmk: use x_ instead of err, where appropriate

many places in lbmk used err, because older versions
of x_ did not handle globbing properly.

however, use of x_ is preferable on trivial commands.

the only time err() should be called is what it has
to be, when x_ can't work, or when a more useful error
message is needed, for context.

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

include/tree.sh

@@ -322,7 +322,7 @@ check_cmake()
 check_autoconf()
 {
 	(
-	cd "$1" || err "!cd $1"
+	x_ cd "$1"
 	[ -f "bootstrap" ] && x_ ./bootstrap $bootstrapargs
 	[ -f "autogen.sh" ] && x_ ./autogen.sh $autogenargs
 	[ -f "configure" ] && x_ ./configure $autoconfargs; :