Add support for nucleol432 board

LED and UART are working

targets/cortex-m4.json

@@ -3,6 +3,7 @@
 	"llvm-target": "armv7em-none-eabi",
 	"cflags": [
 		"--target=armv7em-none-eabi",
-		"-mfloat-abi=soft"
+		"-mfloat-abi=soft",
+		"-Qunused-arguments"
 	]
 }

targets/nucleo-l432kc.json

@@ -0,0 +1,11 @@
+{
+    "inherits": ["cortex-m4"],
+    "build-tags": ["nucleol432kc", "stm32l432", "stm32l4x2", "stm32l4", "stm32"],
+    "linkerscript": "targets/stm32l4x2.ld",
+    "extra-files": [
+      "src/device/stm32/stm32l4x2.s"
+    ],
+    "flash-method": "openocd",
+    "openocd-interface": "stlink-v2-1",
+    "openocd-target": "stm32l4x"
+  }

targets/stm32l4x2.ld

@@ -0,0 +1,10 @@
+
+MEMORY
+{
+  FLASH_TEXT (rx) : ORIGIN = 0x08000000, LENGTH = 256K
+  RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 64K
+}
+
+_stack_size = 4K;
+
+INCLUDE "targets/arm.ld"