Hello,
I see this build error in linux-next (config attached).
[ 4939s] LD vmlinux
[ 4959s] BTFIDS vmlinux
[ 4959s] FAILED unresolved symbol cubictcp_state
[ 4960s] make[1]: ***
[/home/abuild/rpmbuild/BUILD/kernel-vanilla-5.12~rc8.next.20210422/linux-5.12-rc8-next-20210422/Makefile:1277:
vmlinux] Error 255
[ 4960s] make: *** [../Makefile:222: __sub-make] Error 2