Cleaned up Wasm cmake (#13106)

### Summary
Before, if dependencies for the API were not enabled in the cmake
command, you would get linking errors when trying to compile. Now, if
EXECUTORCH_BUILD_WASM is turned on, an error will occur during configure
stage if dependencies were not enabled.

Also changed the API to use executorch_kernels rather than hardcoding in
portable_ops_lib.

For the unit tests, changed the libraries to PRIVATE instead of PUBLIC
and to use `--pre-js` instead of `--post-js` as that is the recommended
way of interfacing with the Embind Module.

### Test plan
```bash
bash scripts/build_wasm_tests.sh
cd cmake-out-wasm/extension/wasm/test/
npm test # after installing Jest
```

Author: Conarnar

extension/wasm/CMakeLists.txt

@@ -37,7 +37,6 @@ list(
   embind
   executorch_core
   extension_data_loader
-  portable_ops_lib
   extension_module_static
   extension_tensor
   extension_runner_util
@@ -49,8 +48,12 @@ target_compile_options(executorch_wasm PUBLIC ${_common_compile_options})
 target_include_directories(
   executorch_wasm PUBLIC ${_common_include_directories}
 )
-target_link_libraries(executorch_wasm PUBLIC ${link_libraries})
+target_link_libraries(
+  executorch_wasm
+  PUBLIC ${link_libraries}
+  INTERFACE executorch_kernels
+)
 
-if(EXECUTORCH_BUILD_WASM_TESTS)
+if(BUILD_TESTING)
   add_subdirectory(test)
 endif()

extension/wasm/test/CMakeLists.txt

@@ -41,13 +41,13 @@ add_custom_target(
 )
 
 add_executable(executorch_wasm_tests)
-target_link_libraries(executorch_wasm_tests PUBLIC executorch_wasm)
+target_link_libraries(executorch_wasm_tests PRIVATE executorch_wasm)
 target_link_options(
   executorch_wasm_tests
-  PUBLIC
+  PRIVATE
   --embed-file
   "${MODELS_DIR}@/"
-  --post-js
+  --pre-js
   ${CMAKE_CURRENT_SOURCE_DIR}/unittests.js
   -sASSERTIONS=2
 )

extension/wasm/test/unittests.js

@@ -6,9 +6,9 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-let et;
+var Module = {};
+const et = Module;
 beforeAll((done) => {
-    et = Module;
     et.onRuntimeInitialized = () => {
         done();
     }

scripts/build_wasm_tests.sh

@@ -11,11 +11,10 @@ cd "$(dirname "${BASH_SOURCE[0]}")/../"
 emcmake cmake . -DEXECUTORCH_BUILD_WASM=ON \
     -DEXECUTORCH_BUILD_EXTENSION_DATA_LOADER=ON \
     -DEXECUTORCH_BUILD_EXTENSION_FLAT_TENSOR=ON \
-    -DEXECUTORCH_BUILD_DEVTOOLS=ON \
     -DEXECUTORCH_BUILD_EXTENSION_MODULE=ON \
     -DEXECUTORCH_BUILD_EXTENSION_TENSOR=ON \
-    -DEXECUTORCH_BUILD_EXTENSION_RUNNER_UTIL=ON \
-    -DEXECUTORCH_BUILD_WASM_TESTS=ON \
+    -DEXECUTORCH_SELECT_OPS_LIST="aten::mm.out,aten::add.out" \
+    -DEXECUTORCH_BUILD_TESTS=ON \
     -DCMAKE_BUILD_TYPE=Release \
     -B"${CMAKE_OUT}"
 

tools/cmake/preset/default.cmake

@@ -152,6 +152,9 @@ define_overridable_option(
   EXECUTORCH_COREML_BUILD_EXECUTOR_RUNNER "Build CoreML executor runner." BOOL
   OFF
 )
+define_overridable_option(
+  EXECUTORCH_BUILD_WASM "Build the ExecuTorch JavaScript API" BOOL OFF
+)
 
 if(EXECUTORCH_BUILD_ARM_BAREMETAL)
   set(_default_executorch_build_pthreadpool OFF)
@@ -321,6 +324,11 @@ check_conflicting_options_on(
   IF_ON EXECUTORCH_SELECT_OPS_LIST CONFLICTS_WITH EXECUTORCH_SELECT_OPS_MODEL
 )
 
+check_required_options_on(
+  IF_ON EXECUTORCH_BUILD_WASM REQUIRES EXECUTORCH_BUILD_EXTENSION_MODULE
+  EXECUTORCH_BUILD_EXTENSION_TENSOR
+)
+
 if(NOT EXISTS ${EXECUTORCH_PAL_DEFAULT_FILE_PATH})
   message(
     FATAL_ERROR