nrf: add microbit-s110v8 target

This makes it possible to use Bluetooth on the BBC micro:bit.

Note that you need to use -programmer=cmsis-dap otherwise the SoftDevice
will be erased while flashing something that uses Bluetooth.

Makefile

@@ -229,6 +229,8 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=microbit            examples/echo
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=microbit-s110v8     examples/echo
+	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=nrf52840-mdk        examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10031            examples/blinky1

targets/microbit-s110v8.json

@@ -0,0 +1,3 @@
+{
+	"inherits": ["microbit", "nrf51-s110v8"]
+}

targets/nrf51-s110v8.json

@@ -0,0 +1,4 @@
+{
+	"build-tags": ["softdevice", "s110v8"],
+	"linkerscript": "targets/nrf51-s110v8.ld"
+}

targets/nrf51-s110v8.ld

@@ -0,0 +1,12 @@
+
+MEMORY
+{
+    /* This SoftDevice requires 96K flash and 8K RAM according to the release
+     * notes of version 8.0.0 */
+    FLASH_TEXT (rw) : ORIGIN = 0x00000000 + 96K, LENGTH = 256K - 96K
+    RAM (xrw)       : ORIGIN = 0x20000000 + 8K,  LENGTH = 16K  - 8K
+}
+
+_stack_size = 2K;
+
+INCLUDE "targets/arm.ld"