To use _RegexParser from SwiftSyntax.
* Create 'libswiftCompilerModules_SwiftSyntax.a' which is a subset of
'libswiftCompilerModules.a'
* Link 'lib_InternalSwiftSyntaxParser' to
'libswiftCompilerModules_SwiftSyntax.a'
* Factor out swift runtime linking logic in CMake so that dynamic
libraries can link to Swift runtime, in addition to executables
* Link 'lib_InternalSwiftSyntaxParser' to swift runtime