zfs-2.4.0-rc.4 Linux 6.18.0, kasan_flag_enabled GPL-only

[smira]

When trying to build zfs-2.4.0-rc.4 (with META file patched to support Linux 6.18) with LInux 6.18.0 for arm64 with CONFIG_KASAN_HW_TAGs=y, the following problem appears at the end of the build:

2025-12-03T12:53:31.8245923Z #96 66.06   LD [M]  spl.o
2025-12-03T12:53:36.1223263Z #96 70.35   LD [M]  zfs.o
2025-12-03T12:53:36.8174799Z #96 71.05   MODPOST Module.symvers
2025-12-03T12:53:37.0729150Z #96 71.31 ERROR: modpost: GPL-incompatible module zfs.ko uses GPL-only symbol 'kasan_flag_enabled'