make cmake target default for emscripten, check for emsdk in Makefile

Author: austinvhuang

experimental/wasm/emscripten/Makefile

@@ -1,19 +1,23 @@
-
 FLAGS=--target=wasm32 -nostdlib -Wl,--no-entry -Wl,--export-all -Wl,--import-memory -Wl,--allow-undefined -fexceptions -std=c++17 -O3
 
+# For all targets, make sure emsdk is installed and `source emsdk_env.sh` is run in the emsdk directory
 
-# Make sure you have:
-# 1) emsdk installed
-# 2) `source emsdk_env.sh` in the emsdk directory
-build/run.wasm:
-	em++ -sUSE_WEBGPU=1 -sUSE_GLFW=3 run.cpp -o build/run.wasm
 
-cmake:
+.PHONY: cmake check-emsdk browser clean
+
+# make clean explicit here because custom_shell.html changes don't trigger a rebuild
+cmake: check-emsdk clean
 	emcmake cmake -B build && cmake --build build -j4
 	npx http-server
 
+build/run.wasm: check-emsdk run.cpp
+	em++ -sUSE_WEBGPU=1 -sUSE_GLFW=3 run.cpp -o build/run.wasm
+
 browser:
 	open http://127.0.0.1:8000/build/run.html
 
 clean:
 	rm -rf build/*
+
+check-emsdk:
+	@which emcc > /dev/null || (echo "emsdk not found. Please install emsdk and run 'source emsdk_env.sh' in the emsdk directory." && exit 1)