Out of all operating systems ever supported by Swift, only Ubuntu 14.04
had libstdc++ 4.8, and Swift has sunset support for Ubuntu 14.04 for a
while now.
* A bunch of them require objc_interop because they import code containing
Objective-C.
* Many others fail on Ubuntu 14.04 because the C++ there doesn't have a
functional std::regex implementation which is required by the
`complete-test` tool.
It may be possible to adjust some of these tests in the future to not
need these extra requirements, but this is a straightforward way to
clean up Linux test results for now.
We won't try to avoid the stdlib completely, but at least try not to
check method names on types that might change in the future.
For rdar://problem/24621131
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.
