build: repair build after swiftlang/swift-tools-support-core#117

Remove `Triple.swift` as tools-support-core now has this defined.  This repairs the CMake based build.

Author: compnerd

Sources/SPMBuildCore/CMakeLists.txt

@@ -11,8 +11,7 @@ add_library(SPMBuildCore
   BuildSystem.swift
   BuiltTestProduct.swift
   Sanitizers.swift
-  Toolchain.swift
-  Triple.swift)
+  Toolchain.swift)
 # NOTE(compnerd) workaround for CMake not setting up include flags yet
 set_target_properties(SPMBuildCore PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})