Merge branch 'bugfix/env_var_SDKCONFIG_DEFAULTS_fail_with_bootloader_subproject_v4.4' into 'release/v4.4'

build_system: stop looking for env var `SDKCONFIG_DEFAULTS` in bootloader subproject (v4.4)

See merge request espressif/esp-idf!21975

tools/cmake/project.cmake

@@ -340,7 +340,14 @@ macro(project project_name)
     # PROJECT_NAME is taken from the passed name from project() call
     # PROJECT_DIR is set to the current directory
     # PROJECT_VER is from the version text or git revision of the current repo
-    set(_sdkconfig_defaults "$ENV{SDKCONFIG_DEFAULTS}")
+
+    # SDKCONFIG_DEFAULTS environment variable may specify a file name relative to the root of the project.
+    # When building the bootloader, ignore this variable, since:
+    # 1. The bootloader project uses an existing SDKCONFIG file from the top-level project
+    # 2. File specified by SDKCONFIG_DEFAULTS will not be found relative to the root of the bootloader project
+    if(NOT BOOTLOADER_BUILD)
+        set(_sdkconfig_defaults "$ENV{SDKCONFIG_DEFAULTS}")
+    endif()
 
     if(NOT _sdkconfig_defaults)
         if(EXISTS "${CMAKE_SOURCE_DIR}/sdkconfig.defaults")