Non-Darwin SDKs product results in per-arch directories.

Depends on swiftlang/swift#19432

Unix (other than Darwin) and Windows do not support fat binaries.
However, the build system was placing the build results in the
platform/OS folder, instead of the per-architecture folder. Having two
architectures side by side was impossible.

After applying the above patch in the Swift compiler, non-Darwin
platforms will look into the per-architecture folders, so the sibling
projects need to leave the products in the right place.

Author: drodriguez

CMakeLists.txt

@@ -72,7 +72,14 @@ if(ENABLE_SWIFT)
                           IMPORTED_LOCATION
                            ${SWIFT_RUNTIME_LIBDIR}/${CMAKE_SHARED_LIBRARY_PREFIX}swiftSwiftOnoneSupport${CMAKE_SHARED_LIBRARY_SUFFIX})
 
-  set(INSTALL_TARGET_DIR "${INSTALL_LIBDIR}/swift/${SWIFT_OS}" CACHE PATH "Path where the libraries will be installed")
+  if(CMAKE_SYSTEM_NAME STREQUAL Darwin)
+    set(INSTALL_TARGET_DIR_default "${INSTALL_LIBDIR}/swift/${SWIFT_OS}")
+  else()
+    set(INSTALL_TARGET_DIR_default "${INSTALL_LIBDIR}/swift/${SWIFT_OS}/${SWIFT_HOST_ARCH}")
+  endif()
+
+  set(INSTALL_TARGET_DIR "${INSTALL_TARGET_DIR_default}" CACHE PATH "Path where the libraries will be installed")
+  set(INSTALL_RSRC_DIR "${INSTALL_LIBDIR}/swift/${SWIFT_OS}/${SWIFT_HOST_ARCH}" CACHE PATH "Path where the compiler resources will be installed")
   set(INSTALL_DISPATCH_HEADERS_DIR "${INSTALL_LIBDIR}/swift/dispatch" CACHE PATH "Path where the headers will be installed for libdispatch")
   set(INSTALL_BLOCK_HEADERS_DIR "${INSTALL_LIBDIR}/swift/Block" CACHE PATH "Path where the headers will be installed for the blocks runtime")
   set(INSTALL_OS_HEADERS_DIR "${INSTALL_LIBDIR}/swift/os" CACHE PATH "Path where the os/ headers will be installed")

src/CMakeLists.txt

@@ -236,6 +236,5 @@ if(ENABLE_SWIFT)
             ${CMAKE_CURRENT_BINARY_DIR}/swift/Dispatch.swiftmodule
             ${CMAKE_CURRENT_BINARY_DIR}/swift/Dispatch.swiftdoc
           DESTINATION
-            "${INSTALL_TARGET_DIR}/${SWIFT_HOST_ARCH}")
+            "${INSTALL_RSRC_DIR}")
 endif()
-