u-boot: add HOME env for make invocations to avoid binman/Python problems with older u-boot versions

- this avoids trouble building certain older versions with binman
  - as it tries to `os.path.join(os.getenv('HOME'), 'bin')` and gets a `None` and dies
- naming names: `tinkerboard` & `xt-q8l-v10` (BOARDFAMILY=rockchip), which _actually use_ binman & 22.04 combo

lib/functions/compilation/uboot.sh

@@ -214,6 +214,7 @@ function compile_uboot_target() {
 		"CCACHE_BASEDIR=$(pwd)"
 		"PATH=${toolchain}:${toolchain2}:${PATH}"
 		"PYTHONPATH=\"${PYTHON3_INFO[MODULES_PATH]}:${PYTHONPATH}\"" # Insert the pip modules downloaded by Armbian into PYTHONPATH (needed e.g. for pyelftools)
+		"HOME=${WORKDIR}"                                            # give it a temporary-dir HOME; some Python stuff in old u-boots wants HOME env to be set
 	)
 
 	# workaround when two compilers are needed