CMake: Don't build _CSwiftSyntax module

`SwiftSyntax` module now doesn't have the dependency to `_CSwiftSyntax`
anymore. It's not needed for CMake builds.

Author: rintaro

CMakeLists.txt

@@ -13,9 +13,6 @@ project(SwiftSyntax LANGUAGES C Swift)
 set(SWIFT_VERSION 5)
 set(CMAKE_Swift_LANGUAGE_VERSION ${SWIFT_VERSION})
 
-# ensure Swift compiler can find _CSwiftSyntax
-add_compile_options($<$<COMPILE_LANGUAGE:Swift>:-I$<SEMICOLON>${CMAKE_CURRENT_SOURCE_DIR}/Sources/_CSwiftSyntax/include>)
-
 set(CMAKE_Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/swift)
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)

Sources/CMakeLists.txt

@@ -6,7 +6,6 @@
 # See http://swift.org/LICENSE.txt for license information
 # See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 
-add_subdirectory(_CSwiftSyntax)
 add_subdirectory(SwiftSyntax)
 add_subdirectory(SwiftDiagnostics)
 add_subdirectory(SwiftParser)

Sources/SwiftSyntax/CMakeLists.txt

@@ -8,7 +8,6 @@
 
 add_library(SwiftSyntax STATIC
   AbsolutePosition.swift
-  AtomicCounter.swift
   BumpPtrAllocator.swift
   IncrementalParseTransition.swift
   SourceLength.swift
@@ -56,9 +55,6 @@ add_library(SwiftSyntax STATIC
   gyb_generated/syntax_nodes/SyntaxTypeNodes.swift
 )
 
-target_link_libraries(SwiftSyntax PRIVATE
-  _CSwiftSyntax)
-
 set_property(GLOBAL APPEND PROPERTY SWIFTSYNTAX_EXPORTS SwiftSyntax)
 
 # NOTE: workaround for CMake not setting up include flags yet