Previously 'isSystemModule()' returns true only if the module is:
- Standard library
- Clang module and that is `IsSystem`
- Swift overlay for clang `IsSystem` module
Now:
- Clang module and that is `IsSystem`; or
- Swift overlay for clang `IsSystem` module
- Swift module found in either of these directories:
- Runtime library directoris (including stdlib)
- Frameworks in `-Fsystem` directories
- Frameworks in `$SDKROOT/System/Library/Frameworks/` (Darwin)
- Frameworks in `$SDKROOT/Library/Frameworks/` (Darwin)
rdar://problem/50516314
I noticed in a follow-up patch that if you just swiftc without passing Onone
these flags are not set and sometimes happen to default to right thing ... or
not; as can be seen by the test cases modified. For example, at Onone we are
supposed to include an extra swift module "SwiftOnoneSupport".
The code goes into its own sub-tree under 'tools' but tests go under 'test',
so that running 'check-swift' will also run all the SourceKit tests.
SourceKit is disabled on non-darwin platforms.
