Create a build error if no bootloader is specified. (#16181)

* Create a build error if no bootloader is specified.

* Update builddefs/bootloader.mk

Co-authored-by: Ryan <fauxpark@gmail.com>

Co-authored-by: Ryan <fauxpark@gmail.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/platforms/avr/bootloaders/custom.c b/platforms/avr/bootloaders/custom.c
new file mode 100644
index 0000000000..624fbe242a
--- /dev/null
+++ b/platforms/avr/bootloaders/custom.c
@@ -0,0 +1,19 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "bootloader.h"
+
+__attribute__((weak)) void bootloader_jump(void) {}