build: use a single top-level Swift module directory

Rather than have a swift module directory that you need to find for each
library, use a single global swift module directory similar to the
runtime output directory.  This will be useful for a follow up change to
enable tests.

Author: compnerd

CMakeLists.txt

@@ -29,6 +29,7 @@ else()
   set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 endif()
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+set(CMAKE_Swift_MODULE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/swift)
 
 include(SwiftSupport)
 

Sources/Yams/CMakeLists.txt

@@ -22,9 +22,8 @@ target_link_libraries(Yams PRIVATE
   CYaml
   ${CORELIBS_FOUNDATION})
 set_target_properties(Yams PROPERTIES
-  Swift_MODULE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/swift
   INTERFACE_COMPILE_OPTIONS "SHELL:-Xcc -I$<TARGET_PROPERTY:CYaml,INCLUDE_DIRECTORIES>"
-  INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_CURRENT_BINARY_DIR}/swift)
+  INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})
 
 set_property(GLOBAL APPEND PROPERTY YAMS_EXPORTS Yams)
 get_swift_host_arch(swift_arch)