…cherrypick

[6.0] Add new include path into Foundation when building tests

The most recent versions of `parse_version` throw an exception if the
version is empty. The version passed in is only set on Darwin (call to
`mac_ver()`, so it's causing test failures on newer versions of Linux
since the test suite can't even start.

Now, the only reason for the version parse is because the tests are
looking at whether or not concurrency is available on the OS. This is
only a limitation if we're working with Darwin. Swift 5.10 on Windows
and Linux always have a Swift 5.10 concurrency runtime, so we don't even
need to check for a version.

rdar://128502662
(cherry picked from commit 65e6ecd)
(cherry picked from commit f26bc21)

…d8f73317d7b7c019bf016ca5bc33

[6.0.1] Guard parse_version