https://github.com/cfillion/reapack/wiki

Download these files into the vendor directory:

1. reaper_plugin.h from Jeff0S/sws
2. catch.hpp from philsquared/Catch
3. WDL from Cockos: git clone http://www-dev.cockos.com/wdl/WDL.git vendor/WDL
4. reaper_plugin_functions.h from the REAPER action "[developer] Write C++ API functions header"

The vendor directory structure should be as follow:

reapack> tree vendor
vendor
├── WDL/
│   └── WDL/
│       ├── MersenneTwister.h
│       ├── adpcm_decode.h
│       ├── adpcm_encode.h
│       ├── assocarray.h
│       └── ...
├── catch.hpp
├── reaper_plugin.h
└── reaper_plugin_functions.h

1. Install Homebrew and Xcode Command Line Tools
2. Install tup and boost: brew tap homebrew/fuse && brew install tup boost
3. Run rake from this directory
4. Copy or link x64/bin/reaper_reapack64.dylib or x64/bin/reaper_reapack32.dylib to REAPER's extension directory

1. Install Ruby for Windows, tup (explicit-variant branch, see this thread) and Visual Studio 2015, with Visual C++
2. Prevent Microsoft's C++ compiler from saving telemetry outside of the build directory: instructions here or set the OptIn registry key to 0 in HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\VSCommon\14.0\SQM
3. Download the latest boost and copy the boost subdirectory into <reapack>\vendor
4. Download the latest curl source code and extract it as vendor/curl:

reapack> tree vendor
vendor
├── curl/
│   ├── builds/
│   │   └── ...
│   ├── winbuild/
│   │   ├── Makefile.vc
│   │   └── ...
│   └── ...
└── ...

5. Download the latest stable amalgamation build of sqlite. Put sqlite3.h and sqlite3.c in <reapack>\vendor.
6. Run build_deps.bat and rake from this directory using "Developer Command Prompt for VS2015"
7. Copy or symlink x64\bin\reaper_reapack64.dll or x86\bin\reaper_reapack32.dll to your REAPER plugin folder