Fix that the `file` fields in ConstExtract JSON output are all prefix
mapped path when caching and prefix mapping are all enabled. This can
cause the consumers of the output failed to find the source file.
Now the JSON file is correct updated with the correct source file
location when caching is on. This allows both un-prefix-mapped source
location and relocatable source file location. As a bonus, now CAS
stores the compact version of the JSON file to save space without
affecting the pretty formatted final output file.
rdar://173736094
Previously, const-values output is not supported correctly as it is not
captured correctly as a dependency. The load of the input JSON file is
loaded via file system directly, that can cause issues like:
* False cache hit when the file is changed
* Cannot be prefix mapped to allow distributed caching
Try to support the input file by:
* Correctly capture the input
* Create a new driver flag `-const-gather-protocols-list` that can do
path remapping correctly in swift-driver
rdar://169109358
Steven Wu
Zhiyu Zhu/朱智语
James Paolantonio
Quinn Taylor
Artem Chikin