[clang] Fix libclang linking on Solaris

Linking `libclang.so` is currently broken on Solaris:

  ld: fatal: option --version-script requires option -z gnu-version-script-compat to be specified

While Solaris `ld` supports a considerable subset of `--version-script`,
there are some elements of the syntax that aren't.

The fix is equivalent to D78510 <https://reviews.llvm.org/D78510>.

Additionally, use of C-style comments is a GNU extension
that can easily be avoided by using `#` as comment character, which is
supported by GNU `ld`, `gold`, and `lld`.

Tested on `amd64-pc-solaris2.11`, `sparcv9-sun-solaris2.11`,
`x86_64-pc-linux-gnu`.

Differential Revision: https://reviews.llvm.org/D107559