Add Emscripten target to CI

No testing, just making sure it compiles, and keeps on doing so.

Ref: https://github.com/quickjs-ng/quickjs/issues/75

.github/workflows/ci.yml

@@ -336,3 +336,17 @@ jobs:
       - name: stats
         run: |
           make stats
+
+  emscripten:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: mymindstorm/setup-emsdk@v13
+      - name: check emsdk
+        run: emcc -v
+      - name: build
+        run: |
+          emcmake cmake -B build
+          emmake make -C build qjs_wasm -j$(getconf _NPROCESSORS_ONLN)
+      - name: result
+        run: ls -lh build

CMakeLists.txt

@@ -165,6 +165,12 @@ target_include_directories(qjs PUBLIC
     $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
 )
 
+if(EMSCRIPTEN)
+    add_executable(qjs_wasm ${qjs_sources})
+    target_compile_definitions(qjs_wasm PRIVATE ${qjs_defines})
+    target_link_libraries(qjs_wasm m)
+endif()
+
 
 # QuickJS bytecode compiler
 #