The switch from llvm::cl to OptTable (D83530) dropped --version, which
is needed by some users.
This patch also adds a -v alias, which is available in GNU addr2line.
The version dumping is similar to llvm-objcopy --version (exotic):
```
llvm-symbolizer
LLVM (http://llvm.org/):
LLVM version 12.0.0git
Optimized build with assertions.
Default target: x86_64-unknown-linux-gnu
Host CPU: skylake-avx512
```
Reviewed By: dyung, jhenderson
Differential Revision: https://reviews.llvm.org/D85624
