BinUtils: Avoid llvm-strip versions older than Clang 11

Since commit cf82300a63 (BinUtils: Clarify search logic and make it more
consistent, 2021-05-27, v3.21.0-rc1~119^2~2) we correctly prefer the
more-specific name `llvm-strip` over `strip` when using Clang.  However,
`llvm-strip` from Clang versions prior to 11 require extra flags to
strip everything.  Until our `install(TARGETS)` logic learns to add
those flags, avoid using older versions of `llvm-strip` by default.

Fixes: #22785