6.12.19 Compilation fails on Arch

Trying to build 6.12.19 using Arch's default linux-lts PKGBUILD with `linux-6.12-echo.patch`. Patch applies cleanly, but I get the following errors: ``` kernel/sched/bs.c: In function ‘init_sched_fair_class’: kernel/sched/bs.c:894:37: error: ‘sched_balance_softirq’ undeclared (first use in this function); did you mean ‘sched_balance_trigger’? 894 | open_softirq(SCHED_SOFTIRQ, sched_balance_softirq); | ^~~~~~~~~~~~~~~~~~~~~ | sched_balance_trigger kernel/sched/bs.c:894:37: note: each undeclared identifier is reported only once for each function it appears in In file included from kernel/sched/bs.c:769: kernel/sched/balancer.h: At top level: kernel/sched/balancer.h:844:13: warning: ‘nohz_balancer_kick’ used but never defined 844 | static void nohz_balancer_kick(struct rq *rq); | ^~~~~~~~~~~~~~~~~~ kernel/sched/balancer.h:542:13: warning: ‘idle_balance’ defined but not used [-Wunused-function] 542 | static void idle_balance(struct rq *this_rq) | ^~~~~~~~~~~~ make[4]: *** [scripts/Makefile.build:229: kernel/sched/bs.o] Error 1 make[3]: *** [scripts/Makefile.build:478: kernel/sched] Error 2 make[2]: *** [scripts/Makefile.build:478: kernel] Error 2 make[2]: *** Waiting for unfinished jobs.... ```