We no longer need `_InternalSwiftSyntaxParser`, but we do need
`libswiftCore.so`.
Fixes https://github.com/realm/SwiftLint/issues/4501
Add a more useful validation test at the end of the Dockerfile.
In addition to running `swiftlint version`, also actually run the linter
which will exercise the SourceKit codepaths.
Since `_InternalSwiftSyntaxParser` isn't in the search paths when building with the `-static-stdlib` flag, we have to manually pass an include path so the swift compiler discovers it. Unfortunately we cannot just pass `-I/usr/lib/swift` because that results in duplicate library errors since the libraries we're linking statically also live there as shared libraries. This first symlinks the module definition to the root of the checkout and uses `.` for the `-I`. Any temporary path could be used instead.
Provides:
- a runtime environment on ubuntu that does not include the Swift toolchain.
- supportintg `docker build https://github.com/realm/SwiftLint.git`
- add `libcurl4-openssl-dev` as build time dependency that introduced by #3058
JP Simard