bootloader: pass legacy header config variable to subproject

components/bootloader/project_include.cmake

@@ -63,6 +63,10 @@ if((NOT CONFIG_SECURE_BOOT_ENABLED) OR
                     -DSECURE_BOOT_SIGNING_KEY=${secure_boot_signing_key}
                     -DPYTHON_DEPS_CHECKED=1
                     -DEXTRA_COMPONENT_DIRS=${CMAKE_CURRENT_LIST_DIR}
+                    # LEGACY_INCLUDE_COMMON_HEADERS has to be passed in via cache variable since
+                    # the bootloader common component requirements depends on this and
+                    # config variables are not available before project() call.
+                    -DLEGACY_INCLUDE_COMMON_HEADERS=${CONFIG_LEGACY_INCLUDE_COMMON_HEADERS}
         INSTALL_COMMAND ""
         BUILD_ALWAYS 1  # no easy way around this...
         BUILD_BYPRODUCTS ${bootloader_binary_files}