Add builds for linux and windows

.gitignore

@@ -7,4 +7,8 @@ merger-app/x64/Debug/*
 !merger-app/x64/Debug/.gitkeep
 
 splitter/build/*
-!splitter/build/.gitkeep
+!splitter/build/.gitkeep
+splitter/build-windows/*
+!splitter/build-windows/.gitkeep
+splitter/build-linux/*
+!splitter/build-linux/.gitkeep

splitter/BUILD.md

@@ -0,0 +1,21 @@
+# How to compile for each platform on macos
+
+1. Install `mingw-w64` and `FiloSottile/musl-cross/musl-cross` via homebrew
+2. Go to splitter directory
+3. Run these command:
+
+```sh
+rm -rf build build-windows build-linux
+touch build/.gitkeep && touch build-windows/.gitkeep && touch build-linux/.gitkeep
+mkdir build && cd $_
+cmake ..
+make
+cd ..
+mkdir build-windows && cd $_
+cmake .. -DCMAKE_SYSTEM_NAME=Windows -DCMAKE_RC_COMPILER=x86_64-w64-mingw32-windres -DCMAKE_C_COMPILER=x86_64-w64-mingw32-gcc -DCMAKE_CXX_COMPILER=x86_64-w64-mingw32-g++
+make
+cd ..
+mkdir build-linux && cd $_
+cmake .. -DCMAKE_SYSTEM_NAME=Linux -DCMAKE_C_COMPILER=x86_64-linux-musl-gcc -DCMAKE_CXX_COMPILER=x86_64-linux-musl-g++
+make
+```