Ensure that modules are installed into the correct path

Author: jmschonfeld

CMakeLists.txt

@@ -33,6 +33,14 @@ endif()
 project(Foundation
     LANGUAGES C Swift)
 
+if(NOT SWIFT_SYSTEM_NAME)
+  if(CMAKE_SYSTEM_NAME STREQUAL Darwin)
+    set(SWIFT_SYSTEM_NAME macosx)
+  else()
+    set(SWIFT_SYSTEM_NAME "$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>")
+  endif()
+endif()
+
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)