LLVM 21 compatibility issue with swab.h

[Theron York]

Hello,

Building Linux kernel 7.0.6 on Gentoo with LLVM  fails:
  error: unknown type name '__attribute_const__'

Setup:
- Gentoo Linux
- LLVM 21 (clang)
- musl libc
- x86_64

Workaround:
  sed -i 's/__attribute_const__/__attribute__((const))/g' 
./include/uapi/linux/swab.h


Thanks,
Theron York