Add support for Clang built Kernels

[ptr1337]

Hi together,

On CachyOS we want to move forward to clang built kernels as default and investigating currently a bunch of dkms modules.
See: CachyOS/linux-cachyos#286

rtw89 with LLVM 18 is failing with following:

DKMS make.log for rtw89-r1090.d1fced1 for kernel 6.10.7-2-cachyos-lto (x86_64)
Fri Aug 30 16:21:38 HKT 2024
make: Entering directory '/usr/lib/modules/6.10.7-2-cachyos-lto/build'
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/core.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/mac80211.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/mac.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/mac_be.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/phy.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/phy_be.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/fw.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/cam.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/efuse.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/efuse_be.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/regd.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/sar.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/coex.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/ps.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/chan.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/debug.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/ser.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/wow.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/acpi.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/rtw8851b.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/rtw8851b_table.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/rtw8851b_rfk.o
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/rtw8851b_rfk_table.o
/var/lib/dkms/rtw89/r1090.d1fced1/build/coex.c:322:49: error: use of undeclared identifier 'reg_num'
  322 |         struct rtw89_btc_fbtc_mreg regs[] __counted_by(reg_num);
      |                                                        ^
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/rtw8851be.o
1 error generated.
make[2]: *** [scripts/Makefile.build:244: /var/lib/dkms/rtw89/r1090.d1fced1/build/coex.o] Error 1
make[2]: *** Waiting for unfinished jobs....
  CC [M]  /var/lib/dkms/rtw89/r1090.d1fced1/build/rtw8852a.o
make[1]: *** [/usr/lib/modules/6.10.7-2-cachyos-lto/build/Makefile:1937: /var/lib/dkms/rtw89/r1090.d1fced1/build] Error 2
make: *** [Makefile:240: __sub-make] Error 2
make: Leaving directory '/usr/lib/modules/6.10.7-2-cachyos-lto/build'

Would be cool to have this fixed.