ARM: 9289/1: Allow pre-ARMv5 builds with ld.lld 16.0.0 and newer

Commit 6a7ee50f

 ("ARM: disallow pre-ARMv5 builds with ld.lld")
prevented v4 or v4t kernels when ld.lld will link the kernel due to
inserting unsupported blx instructions.

ld.lld has been fixed in current main (16.0.0) to avoid inserting these
instructions by inserting position independent thunks instead. Allow
these configurations to be enabled when ld.lld 16.0.0 is used to link
the kernel.

Additionally, add a link to the upstream LLVM issue so that the reason
for this dependency is clearly documented.

Link: https://github.com/ClangBuiltLinux/linux/issues/964
Link: https://github.com/llvm/llvm-project/commit/6f9ff1beee9d12aca0c9caa9ae0051dc6d0a718c

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>