CI: Restore Tufty 2040 board def.

Set the PICO_BOARD_HEADER_DIRS environment variable as per https://github.com/raspberrypi/pico-sdk/blob/master/src/boards/generic_board.cmake

Add our local search path alongside the existing Pico SDK boards dir.

.github/workflows/micropython.yml

@@ -75,7 +75,7 @@ jobs:
         - name: picolipo_16mb
           board: PIMORONI_PICOLIPO_16MB
         - name: tufty2040
-          board: PICO
+          board: PIMORONI_TUFTY2040
         - name: picow
           board: PICO_W
         - name: enviro
@@ -92,6 +92,7 @@ jobs:
     env:
       # MicroPython version will be contained in github.event.release.tag_name for releases
       RELEASE_FILE: pimoroni-${{matrix.name}}-${{github.event.release.tag_name || github.sha}}-micropython
+      PICO_BOARD_HEADER_DIRS: micropython/lib/pico-sdk/src/boards/include/boards;pimoroni-pico-${{ github.sha }}/micropython/board/inc
 
     steps:
     - name: Compiler Cache

micropython/board/inc/pimoroni_tufty2040.h

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+// -----------------------------------------------------
+// NOTE: THIS HEADER IS ALSO INCLUDED BY ASSEMBLER SO
+//       SHOULD ONLY CONSIST OF PREPROCESSOR DIRECTIVES
+// -----------------------------------------------------
+
+#ifndef _BOARDS_PIMORONI_TUFTY_2040_H
+#define _BOARDS_PIMORONI_TUFTY_2040_H
+
+// For board detection
+#define PIMORONI_TUFTY_2040
+
+// --- LED ---
+#ifndef PICO_DEFAULT_LED_PIN
+#define PICO_DEFAULT_LED_PIN 25
+#endif
+// no PICO_DEFAULT_WS2812_PIN
+
+// --- I2C ---
+#ifndef PICO_DEFAULT_I2C
+#define PICO_DEFAULT_I2C 0
+#endif
+#ifndef PICO_DEFAULT_I2C_SDA_PIN
+#define PICO_DEFAULT_I2C_SDA_PIN 4
+#endif
+#ifndef PICO_DEFAULT_I2C_SCL_PIN
+#define PICO_DEFAULT_I2C_SCL_PIN 5
+#endif
+
+// --- SPI ---
+#ifndef PICO_DEFAULT_SPI
+#define PICO_DEFAULT_SPI 0
+#endif
+#ifndef PICO_DEFAULT_SPI_SCK_PIN
+#define PICO_DEFAULT_SPI_SCK_PIN 18
+#endif
+#ifndef PICO_DEFAULT_SPI_TX_PIN
+#define PICO_DEFAULT_SPI_TX_PIN 19
+#endif
+#ifndef PICO_DEFAULT_SPI_RX_PIN
+#define PICO_DEFAULT_SPI_RX_PIN 16
+#endif
+#ifndef PICO_DEFAULT_SPI_CSN_PIN
+#define PICO_DEFAULT_SPI_CSN_PIN 17
+#endif
+
+// --- FLASH ---
+#define PICO_BOOT_STAGE2_CHOOSE_W25Q080 1
+
+#ifndef PICO_FLASH_SPI_CLKDIV
+#define PICO_FLASH_SPI_CLKDIV 2
+#endif
+
+#ifndef PICO_FLASH_SIZE_BYTES
+#define PICO_FLASH_SIZE_BYTES (8 * 1024 * 1024)
+#endif
+
+// All boards have B1 RP2040
+#ifndef PICO_RP2040_B0_SUPPORTED
+#define PICO_RP2040_B0_SUPPORTED 0
+#endif
+
+#endif