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

@@ -133,18 +133,24 @@ add_custom_target(check-xctest
 
 string(TOLOWER ${CMAKE_SYSTEM_NAME} SWIFT_OS)
 
+get_swift_host_arch(SWIFT_HOST_ARCH)
+
 install(FILES
           ${CMAKE_CURRENT_BINARY_DIR}/swift/XCTest.swiftdoc
           ${CMAKE_CURRENT_BINARY_DIR}/swift/XCTest.swiftmodule
         DESTINATION
-          ${CMAKE_INSTALL_FULL_LIBDIR}/swift/${SWIFT_OS}/${CMAKE_SYSTEM_PROCESSOR})
+          ${CMAKE_INSTALL_FULL_LIBDIR}/swift/${SWIFT_OS}/${SWIFT_HOST_ARCH})
 install(FILES
           ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_SHARED_LIBRARY_PREFIX}XCTest${CMAKE_SHARED_LIBRARY_SUFFIX}
         DESTINATION
           ${CMAKE_INSTALL_FULL_LIBDIR})
 # NOTE(compnerd) stage a compatibility copy in the swift resource dir
+if(CMAKE_SYSTEM_NAME STREQUAL Darwin)
+  set(DESTINATION_DIR ${CMAKE_INSTALL_FULL_LIBDIR}/swift/${SWIFT_OS})
+else()
+  set(DESTINATION_DIR ${CMAKE_INSTALL_FULL_LIBDIR}/swift/${SWIFT_OS}/${SWIFT_HOST_ARCH})
+endif()
 install(FILES
           ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_SHARED_LIBRARY_PREFIX}XCTest${CMAKE_SHARED_LIBRARY_SUFFIX}
         DESTINATION
-          ${CMAKE_INSTALL_FULL_LIBDIR}/swift/${SWIFT_OS})
-
+          ${DESTINATION_DIR})

cmake/modules/SwiftSupport.cmake

@@ -131,3 +131,35 @@ function(add_swift_executable executable)
   add_swift_target(${executable} ${ARGN})
 endfunction()
 
+# Returns the current achitecture name in a variable
+#
+# Usage:
+#   get_swift_host_arch(result_var_name)
+#
+# If the current architecture is supported by Swift, sets ${result_var_name}
+# with the sanitized host architecture name derived from CMAKE_SYSTEM_PROCESSOR.
+function(get_swift_host_arch result_var_name)
+  if("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86_64")
+    set("${result_var_name}" "x86_64" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "aarch64")
+    set("${result_var_name}" "aarch64" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc64")
+    set("${result_var_name}" "powerpc64" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc64le")
+    set("${result_var_name}" "powerpc64le" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "s390x")
+    set("${result_var_name}" "s390x" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "armv6l")
+    set("${result_var_name}" "armv6" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "armv7l")
+    set("${result_var_name}" "armv7" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "AMD64")
+    set("${result_var_name}" "x86_64" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "IA64")
+    set("${result_var_name}" "itanium" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86")
+    set("${result_var_name}" "i686" PARENT_SCOPE)
+  else()
+    message(FATAL_ERROR "Unrecognized architecture on host system: ${CMAKE_SYSTEM_PROCESSOR}")
+  endif()
+endfunction()