Currently, the macro plugin options are included as cache key and the
absolute path of the plugin executable and library will affect cache
hit, even the plugin itself is identical.
Using the new option `-resolved-plugin-validation` flag, the macro
plugin paths are remapped just like the other paths during dependency
scanning. `swift-frontend` will unmap to its original path during the
compilation, make sure the content hasn't changed, and load the plugin.
It also hands few other corner cases for macro plugins:
* Make sure the plugin options in the swift module is prefix mapped.
* Make sure the remarks of the macro loading is not cached, as the
mesasge includes the absolute path of the plugin, and is not
cacheable.
rdar://148465899
Use IncludeTreeFileList instead of full feature CASFS for swift
dependency filesystem. This allows smaller CAS based VFS that is smaller
and faster. This is enabled by the CAS enabled compilation does not
need to iterate file system.
rdar://136787368
Build an accurate macro dependency for swift caching. Specifically, do
not include not used macro plugins into the dependency, which might
cause false negatives for cache hits.
This also builds the foundation for future improvement when dependency
scanning will determine the macro plugin to load and swift-frontend do
not need to redo the work.
rdar://127116512
Preliminary caching support for macro:
* Inserting the plugin into the CASFS
* Lookup plugin via physical file system
For future better support, we should teach dependency scanner to resolve
macros and return the resolved plugins to swift-frontend.
rdar://121873571
