ANDROID: arm64: disable BTI with CFI for Clang <12

Older versions of Clang didn't generate BTI instructions for the
compiler-generated CFI check functions. As CFI provides a more
fine-grained control-flow checking then BTI, disable BTI when CFI is
enabled and we're using Clang <12.

Bug: 145210207
Change-Id: I248bc761443e4f354cf4dfbfc3db0fc22385ce63
Link: https://bugs.llvm.org/show_bug.cgi?id=46258
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

arch/arm64/Kconfig

@@ -1627,6 +1627,8 @@ config ARM64_BTI_KERNEL
 	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94697
 	depends on !CC_IS_GCC || GCC_VERSION >= 100100
 	depends on !(CC_IS_CLANG && GCOV_KERNEL)
+	# https://bugs.llvm.org/show_bug.cgi?id=46258
+	depends on !CFI_CLANG || CLANG_VERSION >= 120000
 	depends on (!FUNCTION_GRAPH_TRACER || DYNAMIC_FTRACE_WITH_REGS)
 	help
 	  Build the kernel with Branch Target Identification annotations