* [portfile functions] Override execute_process() to accept ALLOW_IN_DOWNLOAD_MODE option
* [vcpkg install] Set VCPKG_DOWNLOAD_MODE when using --only-downloads option
* [vcpkg_find_acquire_program] Allow in Download Mode
* Don't stop when build fails for a package
* Download sources for all packages in dependency graph
* Improve output messages
* Enable acquiring MSYS packages in download mode
* Documentation
* Update documentation
* execute_process() always fails on Download Mode
* Regenerate docs and fix formatting
* Run clang-format
* Use _execute_process on vcpkg_from_<source> helpers
