lib/tests/update-llvm.sh: update minimum clang version of building bpf selftest

> BTW, I failed to compile the latest selftests/bpf with
> the following errors:
>
> progs/verifier_and.c:58:16: error: invalid operand for instruction
>         asm volatile ("                                 \
>

These tests were moved to use inline assembly recently (2 month ago).
Discussion at the time was whether to use \n\ or \ terminators at the
end of each line. People opted for \ as easier to read.
Replacing \ with \n\ and compiling this test using clang 14 shows
more informative error message:

$ make -j14 `pwd`/verifier_and.bpf.o
  CLNG-BPF [test_maps] verifier_and.bpf.o
progs/verifier_and.c:68:1: error: invalid operand for instruction
        w1 %%= 2;                                       \n\
^
<inline asm>:11:5: note: instantiated into assembly here
        w1 %= 2;

My guess is that clang 14 does not know how to handle operations on
32-bit sub-registers w[0-9].

But using clang 14 I get some errors not related to inline assembly as well.
Also, I recall that there were runtime issues with clang 14 and
tests using enum64.

All-in-all, you need newer version of clang for tests nowadays,
sorry for inconvenience.

Link: https://lore.kernel.org/netdev/[email protected]/
Signed-off-by: Yujie Liu <[email protected]>
Signed-off-by: Philip Li <[email protected]>

Author: Yujie-Liu

lib/tests/update-llvm.sh

@@ -1,13 +1,15 @@
 #!/bin/bash
 
-# As of now, make bpf failed when we use clang under v10.
-# prepare_for_llvm works for cluster, for local user, please install clang v10
+. $LKP_SRC/lib/env.sh
+
+# make bpf failed when we use clang under v15 on v6.7 kernel
+# prepare_for_llvm works for cluster, for local user, please install clang v15 or newer
 # mannually.
 prepare_for_llvm()
 {
 	# Due to some low dependency version issues, the latest version of the llvm_project.cgz package
 	# cannot be generated in alios.
-	# But bpf must use llvm v10 or higher, so don't run bpf on alios.
+	# But bpf must use llvm v15 or higher, so don't run bpf on alios.
 	is_aliyunos && die "alios doesn't support bpf due to some dependency issues"
 
 	#   LLVM version 11.0.1
@@ -16,8 +18,8 @@ prepare_for_llvm()
 	llvm_version=${llvm_version##* }
 	llvm_version=${llvm_version%%.*}
 	echo "llvm_version: $llvm_version"
-	[[ $llvm_version -ge 10 ]] || {
-		echo "Please install llvm-10 or newer before running bpf"
+	[[ $llvm_version -ge 15 ]] || {
+		echo "Please install llvm-15 or newer before running bpf"
 		return 1
 	}
 }