[Core] Add support for RISC-V builds and GD32VF103 MCU (#12508)

* Add support for RISC-V builds and GD32VF103 MCU

* Add toolchain selection in chibios.mk based on the mcu selected in
mcu_selection.mk
* Reorder and added comments to chibios.mk to have a streamlined makefile
* Add GD32VF103 mcu to possible targets for QMK.
* Add STM32 compatibility for GD32VF103 MCU, this is hacky but more efficent
  then rewriting every driver.
* Add GigaDevice DFU bootloader as flash target, please note that
  dfu-util of at least version 0.10 is needed.
* Add analog driver compatibility
* Add apa102 bitbang driver compatibility
* Add ws2812 bitbang driver compatibility
* Add eeprom in flash emulation compatibility
* Allow faster re-builds with ccache

* Add SiPeed Longan Nano to platform files

* Add SiPeed Longan Nano Onekeys

* Make quine compatible with other bootloaders

* Support builds with picolibc

* Add risc-v toolchain to arch and debian/ubuntu scripts

1 files changed, 37 insertions, 0 deletions

diff --git a/keyboards/handwired/onekey/sipeed_longan_nano/config.h b/keyboards/handwired/onekey/sipeed_longan_nano/config.h
new file mode 100644
index 0000000000..1825b936d8
--- /dev/null
+++ b/keyboards/handwired/onekey/sipeed_longan_nano/config.h
@@ -0,0 +1,37 @@
+/* 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 2 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/>.
+ */
+
+#pragma once
+
+#include "config_common.h"
+
+#define MATRIX_COL_PINS \
+    { B0 }
+#define MATRIX_ROW_PINS \
+    { A7 }
+#define UNUSED_PINS
+
+#define BACKLIGHT_PIN A1           /* Green LED. */
+#define BACKLIGHT_PWM_DRIVER PWMD5 /* GD32 numbering scheme starts from 0, TIMER4 on GD32 boards is TIMER5 on STM32 boards. */
+#define BACKLIGHT_PWM_CHANNEL 2    /* GD32 numbering scheme starts from 0, Channel 1 on GD32 boards is Channel 2 on STM32 boards. */
+
+#define RGB_DI_PIN A2
+#define RGB_CI_PIN B13
+
+#define ADC_PIN A0
+
+#define I2C1_CLOCK_SPEED 1000000 /* GD32VF103 supports fast mode plus. */
+#define I2C1_DUTY_CYCLE FAST_DUTY_CYCLE_2