[llvm] [llvm] Add Trusty OSType (PR #210119)

[Fangrui Song via llvm-commits]

MaskRay wrote:

 An OSType is warranted only when it guides TargetInfo/driver/CodeGen/etc.
clang supports arbitrary triples even if there is no dedicated Triple entry.

 If, on inspection, all Trusty actually needs is a set of default command-line options, that belongs in a clang configuration file, not in Triple.

https://github.com/llvm/llvm-project/pull/210119