Fix cross-compiling ios targets with cmake 3.14 as rust-lang#88 states (rust-lang#93)

* Rename target variable to target_triple

* Remove a bit of code duplication

* Add GenericTarget with several override points

* Add support for cross-compiling Apple targets with cmake 3.14

* Removed lazy_static and regex

Co-authored-by: Kyle Fleming <[email protected]>

Author: 2 people