Updater: Use -O0 and write flash writer and fix hex parser

stm-firmware/updater/ram-code/flash-writer.h

@@ -0,0 +1,16 @@
+#ifndef _FLASH_WRITER_H_
+#define _FLASH_WRITER_H_
+
+#include <stdint.h>
+
+void flash_writer_enable_access(void);
+
+void flash_writer_perform_mass_erase(void);
+
+uint32_t flash_writer_get_flash_size(void);
+
+uint32_t flash_writer_get_base_address(void);
+
+int flash_writer_write_to_memory(void *dest, void *src, uint32_t size);
+
+#endif /* _FLASH_WRITER_H_ */