build: restructure the install location handling

Adopt the latest best practices for handling module installation.
Introduce the new `XCTest_INSTALL_NESTED_SUBDIR` option to allow
installation into platform/architecture subdirectory allowing
multi-architecture installations for platforms like Windows and Android.
This is currently opt-in and requires a newer toolchain (something
within the last ~2w) to detect the defaults. The values can be
overridden by the user if desired.

Author: compnerd

CMakeLists.txt

@@ -24,10 +24,13 @@ endif()
 include(SwiftSupport)
 include(GNUInstallDirs)
 include(CheckLinkerFlag)
+include(PlatformInfo)
 
-if(CMAKE_SYSTEM_NAME STREQUAL Linux
-    OR CMAKE_SYSTEM_NAME STREQUAL FreeBSD
-    OR CMAKE_SYSTEM_NAME STREQUAL OpenBSD)
+option(XCTest_INSTALL_NESTED_SUBDIR "Install libraries under a platform and architecture subdirectory" NO)
+set(XCTest_INSTALL_LIBDIR "${CMAKE_INSTALL_LIBDIR}/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>$<$<BOOL:${XCTest_INSTALL_NESTED_SUBDIR}>:/${XCTest_PLATFORM_SUBDIR}/${XCTest_ARCH_SUBDIR}>")
+set(XCTest_INSTALL_SWIFTMODULEDIR "${CMAKE_INSTALL_LIBDIR}/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>$<$<BOOL:${XCTest_INSTALL_NESTED_SUBDIR}>:/${XCTest_PLATFORM_SUBDIR}>")
+
+if(UNIX)
   enable_language(C)
   check_linker_flag(C "LINKER:--build-id=sha1" LINKER_SUPPORTS_BUILD_ID)
 endif()
@@ -142,14 +145,18 @@ endif()
 
 
 set_property(GLOBAL APPEND PROPERTY XCTest_EXPORTS XCTest)
+
+
 get_swift_host_arch(swift_arch)
 install(TARGETS XCTest
-  ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>/$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>
-  LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>/$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>
+  ARCHIVE DESTINATION ${XCTest_INSTALL_LIBDIR}
+  LIBRARY DESTINATION ${XCTest_INSTALL_LIBDIR}
   RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
-install(FILES
-  ${CMAKE_CURRENT_BINARY_DIR}/swift/XCTest.swiftdoc
-  ${CMAKE_CURRENT_BINARY_DIR}/swift/XCTest.swiftmodule
-  DESTINATION ${CMAKE_INSTALL_LIBDIR}/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>/$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>/${swift_arch})
+install(FILES ${CMAKE_CURRENT_BINARY_DIR}/swift/XCTest.swiftdoc
+  DESTINATION ${XCTest_INSTALL_SWIFTMODULEDIR}/XCTest.swiftmodule
+  RENAME ${XCTest_MODULE_TRIPLE}.swiftdoc)
+install(FILES ${CMAKE_CURRENT_BINARY_DIR}/swift/XCTest.swiftmodule
+  DESTINATION ${XCTest_INSTALL_SWIFTMODULEDIR}/XCTest.swiftmodule
+  RENAME ${XCTest_MODULE_TRIPLE}.swiftmodule)
 
 add_subdirectory(cmake/modules)

cmake/modules/PlatformInfo.cmake

@@ -0,0 +1,41 @@
+
+set(pti_command "${CMAKE_Swift_COMPILER}" -print-target-info)
+if(CMAKE_Swift_COMPILER_TARGET)
+  list(APPEND pti_command -target ${CMAKE_Swift_COMPILER_TARGET})
+endif()
+execute_process(COMMAND ${pti_command} OUTPUT_VARIABLE target_info_json)
+message(CONFIGURE_LOG "Swift Target Info: ${pti_command}\n"
+"${target_info_json}")
+
+if(NOT XCTest_MODULE_TRIPLE)
+  string(JSON module_triple GET "${target_info_json}" "target" "moduleTriple")
+  set(XCTest_MODULE_TRIPLE "${module_triple}" CACHE STRING "Triple used for installed swift{doc,module,interface} files")
+  mark_as_advanced(XCTest_MODULE_TRIPLE)
+
+  message(CONFIGURE_LOG "Swift Module Triple: ${module_triple}")
+endif()
+
+if(NOT XCTest_PLATFORM_SUBDIR)
+  string(JSON platform GET "${target_info_json}" "target" "platform")
+  if(NOT platform)
+    if(NOT SWIFT_SYSTEM_NAME)
+      if(CMAKE_SYSTEM_NAME STREQUAL Darwin)
+        set(platform macosx)
+      else()
+        set(platform $<LOWER_CASE:${CMAKE_SYSTEM_NAME}>)
+      endif()
+    endif()
+  endif()
+  set(XCTest_PLATFORM_SUBDIR "${platform}" CACHE STRING "Platform name used for installed swift{doc,module,interface} files")
+  mark_as_advanced(XCTest_PLATFORM_SUBDIR)
+
+  message(CONFIGURE_LOG "Swift Platform: ${platform}")
+endif()
+
+if(NOT XCTest_ARCH_SUBDIR)
+  string(JSON arch GET "${target_info_json}" "target" "arch")
+  set(XCTest_ARCH_SUBDIR "${arch}" CACHE STRING "Architecture used for setting the architecture subdirectory")
+  mark_as_advanced(XCTest_ARCH_SUBDIR)
+
+  message(CONFIGURE_LOG "Swift Architecture: ${arch}")
+endif()