[UBSan] Disable the function and kcfi sanitizers on an execute-only target.

An execute-only target disallows data access to code sections.
-fsanitize=function and -fsanitize=kcfi instrument indirect function
calls to load a type hash before the function label. This results in a
non-execute access to the code section and a runtime error.

To solve the issue, -fsanitize=function should not be included in any
check group (e.g. undefined) on an execute-only target. If a user passes
-fsanitize=undefined, there is no error and no warning. However, if the
user explicitly passes -fsanitize=function or -fsanitize=kcfi on an
execute-only target, an error will be emitted.

Fixes: https://github.com/llvm/llvm-project/issues/64931.

Reviewed By: MaskRay, probinson, simon_tatham

Differential Revision: https://reviews.llvm.org/D158614