Added 'flash_area_get_image_buildnum' to retrieve build #

Author: danielinux

include/flash.h

@@ -130,4 +130,7 @@ int flash_area_get_sectors(int fa_id, uint32_t *count,
 int flash_area_id_from_image_slot(int slot);
 int flash_area_id_to_image_slot(int area_id);
 
+/* Get the build number of the image stored at the begining of the given flash area */
+uint32_t flash_area_get_image_buildnum(const struct flash_area *fap);
+
 #endif /* H_UTIL_FLASH_MAP_ */

lib/bootutil/src/bootutil_misc.c

@@ -772,3 +772,9 @@ uint8_t flash_area_erased_val(const struct flash_area *fap)
     (void)fap;
     return 0xff;
 }
+
+uint32_t flash_area_get_image_buildnum(const struct flash_area *fap)
+{
+    struct image_header *hdr = (struct image_header *)(fap->fa_off);
+    return hdr->ih_ver.iv_build_num;
+}

tools/ed25519/ed25519_sign.c

@@ -145,6 +145,7 @@ int main(int argc, char *argv[])
     hdr->ih_hdr_size = IMAGE_FIRMWARE_OFFSET;
     hdr->ih_img_size = st.st_size;
     hdr->ih_ver.iv_major = version;
+    hdr->ih_ver.iv_build_num = (uint32_t)(st.st_mtime);
 
     /* Sha256 */
     wc_Sha256Update(&sha, (uint8_t *)hdr, IMAGE_FIRMWARE_OFFSET);