Enable emscripten builds to compile slang.dll to WebAssembly. (#5131)

* Compile fixes for Wasm

The issues are all are due to 'long' types being 32 bits on WASM.

- class members redeclared errors
- << with StringBuilder and unsigned long is ambiguous

This helps to address issue #5115.

* Use the host executable suffix for generators

Since the generators are run at build-time, we should not use CMAKE_EXECUTABLE_SUFFIX,
which is the suffix for the target platform.
Instead, define CMAKE_HOST_EXECUTABLE_SUFFIX as appropriate, and use that suffix instead.

This helps to address issue #5115.

* Add support for Wasm as a platform

This helps to address issue #5115.

* Add emscripten build

This closes #5115.

1 files changed, 18 insertions, 0 deletions

diff --git a/CMakePresets.json b/CMakePresets.json
index e87b976bd..7b847e03e 100644
--- a/CMakePresets.json
+++ b/CMakePresets.json
@@ -16,6 +16,16 @@
       }
     },
     {
+      "name": "emscripten",
+      "description": "Emscripten-based Wasm build",
+      "generator": "ninja",
+      "binaryDir": "${sourceDir}/build.em",
+      "cacheVariables": {
+        "SLANG_SLANG_LLVM_FLAVOR": "DISABLE",
+        "CMAKE_EXE_LINKER_FLAGS": "-sASSERTIONS -sALLOW_MEMORY_GROWTH"
+      }
+    },
+    {
       "name": "msvc-base",
       "hidden": true,
       "inherits": "default",
@@ -75,6 +85,14 @@
       "configuration": "Release"
     },
     {
+      "name": "emscripten",
+      "configurePreset": "emscripten",
+      "configuration": "Release",
+      "targets": [
+        "slang"
+      ]
+    },
+    {
       "name": "generators",
       "inherits": "release",
       "configurePreset": "generators",