Build LLVM (with Wasm) on Windows

win-llvm.txt

Build LLVM (with Wasm) on Windows
---------------------------------

Tested with VS2019 (probably works with older versions). See here for original instructions:

	https://emscripten.org/docs/building_from_source/index.html
	http://llvm.org/docs/CMake.html

Make sure you have CMake (tested with 3.15.5), Ninja (tested with 1.9.0) and Git installed and on your Path.

1. Launch the "x64 Native Tools" command prompt for VS. Don't skip this.

2. Checkout LLVM:

	git clone --config core.autocrlf=false https://github.com/llvm/llvm-project.git \Path\To\LLVM

3. Create the CMake Ninja generator, building for 'all' targets or alternatively just for -DLLVM_TARGETS_TO_BUILD="WebAssembly":

	cd \Path\To\LLVM
	mkdir build
	cd build
	cmake -G Ninja ../llvm -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS='lld;clang' -DLLVM_INCLUDE_EXAMPLES=OFF -DLLVM_INCLUDE_TESTS=OFF

4. Build it! Probably best to go for lunch or something:

	cmake --build .

5. Any 'host' errors, missing includes, etc., are probably down you skipping step 1.

6. Open the %HOMEPATH%\.emscripten config file and point LLVM_ROOT to the generated binaries:

	LLVM_ROOT = "C:\Path\To\LLVM\build\bin"

That's it!

TODO: why aren't we building libcxx?