...to remove the temptation to put everything in one file with the same
name as the module. This doesn't do anything for overlays that /already/
have everything in one file with the same name as the module, except for
a few easy cases; we can unpack the rest later.
os/activity.h or os/log.h. Update cmake files again, hardcoding a Darwin
dependency. The script does not notice that Foundation depends on
CoreGraphics, so add that manually.
Also found that MapKit is supported on WATCHOS but we didn't have dependencies
for that.
Favor one line per supported SDK instead of catch-all dependency lines.
Distinguish from SDKs which have no dependencies vs SDKs which are
unsupported on a particular platform by printing `unsupported` to the
console and remove the line in the cmake file because it should
not exist anyway.
This full cleanup was not done before because of circularity detected by the
util, which has since been fixed.
Support directories with spaces.
From the Swift documentation:
"If you define an optional variable without providing a default value,
the variable is automatically set to nil for you."
