build-llvm.py: Update GOOD_REVISION to 81c5d468cf00d6e41112fba6c89d6c40013bcbda

This has been lightly qualified on an aarch64 and x86_64 host with the
environment and configuration that I build the kernel.org toolchains
with.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Author: nathanchance

build-llvm.py

@@ -22,7 +22,7 @@
     BOOL_ARGS = {'action': 'store_true'}
 
 # This is a known good revision of LLVM for building the kernel
-GOOD_REVISION = '3c0f7b184d265281dfcd4fab73348bc0e72c9902'
+GOOD_REVISION = '81c5d468cf00d6e41112fba6c89d6c40013bcbda'
 
 # The version of the Linux kernel that the script downloads if necessary
 DEFAULT_KERNEL_FOR_PGO = (6, 18, 0)