SDK is provided by the vendor and it is OK to be rebuilt in Ubuntu 20.04 according to the vendor.
I tried to rebuild image on the same environment by vendor document and use the below three steps Step(1)(2) are okay but the error message"cparser_tree.o', needed by 'diag'. Stop." is appeared after executing step(3). The vendor didn't know how to fix the issue and just said it can be rebuilt well in Ubuntu 20.04. I am a rookie in the Linux field. How can I fix the issue?
make preconfig------
make menuconfig
make all
rm -f /home/patrick/Downloads/rtl819x-SDK-usdk-ap-v2.3.1a-full-package/rtl819x/linux-5.10.x/drivers/net/ethernet/realtek/rtl86900/sdk/src/app/diag_rtk/src/diag_debug.o
make[4]: *** No rule to make target '/home/patrick/Downloads/rtl819x-SDK-usdk-ap-v2.3.1a-full-package/rtl819x/linux-5.10.x/drivers/net/ethernet/realtek/rtl86900/sdk/src/app/diag_rtk/src/parser/cparser_tree.o', needed by 'diag'. Stop.
make[4]: *** Waiting for unfinished jobs....
make[4]: Leaving directory '/home/patrick/Downloads/rtl819x-SDK-usdk-ap-v2.3.1a-full-package/rtl819x/linux-5.10.x/drivers/net/ethernet/realtek/rtl86900/sdk/src/app/diag_rtk'
make[3]: *** [/home/patrick/Downloads/rtl819x-SDK-usdk-ap-v2.3.1a-full-package/rtl819x/linux-5.10.x/drivers/net/ethernet/realtek/rtl86900/sdk/build/Makefile.app.list:182: all] Error 1
make[3]: Leaving directory '/home/patrick/Downloads/rtl819x-SDK-usdk-ap-v2.3.1a-full-package/rtl819x/linux-5.10.x/drivers/net/ethernet/realtek/rtl86900/sdk/src/app'
make[2]: *** [Makefile:23: all] Error 2
make[2]: Leaving directory '/home/patrick/Downloads/rtl819x-SDK-usdk-ap-v2.3.1a-full-package/rtl819x/user/diagshell'
/bin/sh: 28: exit: Illegal number: prepare
make[1]: *** [Makefile:907: all] Error 2
make[1]: Leaving directory '/home/patrick/Downloads/rtl819x-SDK-usdk-ap-v2.3.1a-full-package/rtl819x/user'
make: *** [Makefile:944: subdirs] Error 1
