thanks for uboot!

i'm trying to build uboot for raspi 4. these steps produced warnings and a compile error ``` $ git clone https://source.denx.de/u-boot/u-boot.git $ cd u-boot/ $ make CC=clang rpi_4_defconfig HOSTCC scripts/basic/fixdep HOSTCC scripts/kconfig/conf.o YACC scripts/kconfig/zconf.tab.c LEX scripts/kconfig/zconf.lex.c HOSTCC scripts/kconfig/zconf.tab.o HOSTLD scripts/kconfig/conf generated_defconfig:19:warning: unexpected data: # CONFIG_DISPLAY_CPUINFO is not set generated_defconfig:20:warning: unexpected data: # CONFIG_DISPLAY_BOARDINFO is not set generated_defconfig:46:warning: unexpected data: # CONFIG_PINCTRL_GENERIC is not set generated_defconfig:49:warning: unexpected data: # CONFIG_REQUIRE_SERIAL_CONSOLE is not set generated_defconfig:64:warning: unexpected data: # CONFIG_VIDEO_BPP8 is not set generated_defconfig:65:warning: unexpected data: # CONFIG_VIDEO_BPP16 is not set generated_defconfig:70:warning: unexpected data: # CONFIG_HEXDUMP is not set # # configuration written to .config # $ make HOSTCC=clang CROSS_COMPILE=arm-linux-gnueabi- CC=clang HOSTCC scripts/kconfig/conf.o HOSTCC scripts/kconfig/zconf.tab.o HOSTLD scripts/kconfig/conf scripts/kconfig/conf --syncconfig Kconfig UPD include/config.h CFG u-boot.cfg clang: error: unsupported option '-ffixed-x18' for target 'arm-linux-gnueabi' make[1]: *** [scripts/Makefile.autoconf:82: u-boot.cfg] Error 1 make: *** No rule to make target 'include/config/auto.conf', needed by 'include/config/uboot.release'. Stop. ``` ``` $ clang -v Ubuntu clang version 18.1.3 (1ubuntu1) ... ```