build: add a shim for older CMake (#1664)

WASI was introduced into CMake as a platform in 3.31. For older CMake
versions, we add a shim to allow cleanly supporting this platform.

Co-authored-by: Jonathan Grynspan <[email protected]>

Author: compnerd

CMakeLists.txt

@@ -24,8 +24,15 @@ set(SWT_SOURCE_ROOT_DIR ${CMAKE_SOURCE_DIR})
 project(SwiftTesting
   LANGUAGES CXX Swift)
 
+if(CMAKE_VERSION VERSION_LESS 3.31)
+  if(CMAKE_SYSTEM_NAME STREQUAL "Generic" AND CMAKE_SYSTEM_PROCESSOR MATCHES "wasm32")
+    set(CMAKE_SYSTEM_NAME WASI)
+    set(WASI 1)
+  endif()
+endif()
+
 if(NOT APPLE)
-  if(NOT CMAKE_SYSTEM_NAME STREQUAL WASI)
+  if(NOT WASI)
     find_package(dispatch CONFIG)
   endif()
   find_package(Foundation CONFIG)

cmake/modules/shared/CompilerSettings.cmake

@@ -42,7 +42,7 @@ if(NOT APPLE)
   add_compile_definitions("SWT_NO_SNAPSHOT_TYPES")
   add_compile_definitions("SWT_NO_FOUNDATION_FILE_COORDINATION")
 endif()
-if(CMAKE_SYSTEM_NAME STREQUAL "WASI")
+if(WASI)
   add_compile_definitions("SWT_NO_DYNAMIC_LINKING")
   add_compile_definitions("SWT_NO_PIPES")
 endif()
@@ -60,7 +60,7 @@ if(SWT_TESTING_LIBRARY_VERSION)
   add_compile_definitions("$<$<COMPILE_LANGUAGE:CXX>:SWT_TESTING_LIBRARY_VERSION=\"${SWT_TESTING_LIBRARY_VERSION}\">")
 endif()
 
-if((NOT BUILD_SHARED_LIBS) AND (NOT CMAKE_SYSTEM_NAME STREQUAL WASI))
+if((NOT BUILD_SHARED_LIBS) AND NOT WASI)
   # When building a static library, Interop is not supported at this time
   add_compile_definitions("SWT_NO_INTEROP")
 endif()