cmake: fix custom bootloader issue

Issue is that when users creates a custom bootloader from
$IDF_PATH/components/bootloader. Parent project build uses the copy but
bootloader subproject build uses the original still. The issue is solved
by passing the custom bootloader as extra component directory so
bootloader build knows to use the new copy (itself) in the build.

components/bootloader/project_include.cmake

@@ -57,11 +57,12 @@ if((NOT CONFIG_SECURE_BOOT_ENABLED) OR
     idf_build_get_property(idf_target IDF_TARGET)
     externalproject_add(bootloader
         # TODO: support overriding the bootloader in COMPONENT_PATHS
-        SOURCE_DIR "${idf_path}/components/bootloader/subproject"
+        SOURCE_DIR "${CMAKE_CURRENT_LIST_DIR}/subproject"
         BINARY_DIR "${BOOTLOADER_BUILD_DIR}"
         CMAKE_ARGS  -DSDKCONFIG=${sdkconfig} -DIDF_PATH=${idf_path} -DIDF_TARGET=${idf_target}
                     -DSECURE_BOOT_SIGNING_KEY=${secure_boot_signing_key}
                     -DPYTHON_DEPS_CHECKED=1
+                    -DEXTRA_COMPONENT_DIRS=${CMAKE_CURRENT_LIST_DIR}
         INSTALL_COMMAND ""
         BUILD_ALWAYS 1  # no easy way around this...
         BUILD_BYPRODUCTS ${bootloader_binary_files}