begin to integrate SwiftSystem (#437)

tomerd · web-flow · commit dcb61adedfbb · 2021-12-13T08:45:51.000-08:00
motivation: SwiftSystem provides infra that can replace some bespoke implementations in TSC and, improving the cross-platform support. as such we are adding it as a dependency to TSC

changes: add SwiftSystem to CMake setup so it can be included in CMake based builds
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -24,6 +24,7 @@ find_package(SwiftPM QUIET)
 find_package(LLBuild QUIET)
 find_package(ArgumentParser CONFIG REQUIRED)
 find_package(SwiftCollections QUIET)
+find_package(SwiftSystem CONFIG REQUIRED)
 
 include(SwiftSupport)
 
