### Usage

To build dependencies for the current arch+OS:

    make

To build for another arch/OS:

    make HOST=host-platform-triplet

For example:

    make HOST=x86_64-w64-mingw32 -j4

A prefix will be generated that's suitable for plugging into Gridcoin's
CMake build. In the above example, a dir named x86_64-w64-mingw32 will be
created. To use it for Gridcoin:

    cmake -B build --toolchain depends/x86_64-w64-mingw32/toolchain.cmake

Common `host-platform-triplets` for cross compilation are:

- `i686-w64-mingw32` for Win32
- `x86_64-w64-mingw32` for Win64
- `x86_64-apple-darwin` for macOS
- `arm-linux-gnueabihf` for Linux ARM 32 bit
- `aarch64-linux-gnu` for Linux ARM 64 bit

No other options are needed, the paths are automatically configured.

### Install the required dependencies: Ubuntu & Debian

#### For macOS cross compilation

    sudo apt-get install curl librsvg2-bin libtiff-tools bsdmainutils cmake imagemagick libcap-dev libz-dev libbz2-dev python3-setuptools libtinfo5 xorriso

#### For Win64 cross compilation

- see [build-windows.md](../doc/build-windows.md#cross-compilation-for-ubuntu-and-windows-subsystem-for-linux)

#### For Linux (including i386, ARM) cross compilation

Common Linux dependencies:

    sudo apt-get install make automake cmake curl g++-multilib libtool binutils-gold bsdmainutils pkg-config python3 patch bison

For Linux ARM cross compilation:

    sudo apt-get install g++-arm-linux-gnueabihf binutils-arm-linux-gnueabihf

For Linux AARCH64 cross compilation:

    sudo apt-get install g++-aarch64-linux-gnu binutils-aarch64-linux-gnu

### Dependency Options

The following can be set when running make: make FOO=bar

    SOURCES_PATH: downloaded sources will be placed here
    BASE_CACHE: built packages will be placed here
    SDK_PATH: Path where sdk's can be found (used by macOS)
    FALLBACK_DOWNLOAD_PATH: If a source file can't be fetched, try here before giving up
    C_STANDARD: Set the C standard version used. Defaults to `c11`.
    CXX_STANDARD: Set the C++ standard version used. Defaults to `c++17`.
    NO_QT: Don't download/build/cache qt and its dependencies
    NO_WALLET: Don't download/build/cache libs needed to enable the wallet
    NO_UPNP: Don't download/build/cache packages needed for enabling upnp
    DEBUG: disable some optimizations and enable more runtime checking
    HOST_ID_SALT: Optional salt to use when generating host package ids
    BUILD_ID_SALT: Optional salt to use when generating build package ids

If some packages are not built, for example `make NO_WALLET=1`, the appropriate
options will be passed to Gridcoin's CMake configuration.

### Additional targets:

    download: run 'make download' to fetch all sources without building them
    download-osx: run 'make download-osx' to fetch all sources needed for macOS builds
    download-win: run 'make download-win' to fetch all sources needed for win builds
    download-linux: run 'make download-linux' to fetch all sources needed for Linux builds

### Other documentation

- [description.md](description.md): General description of the depends system
- [packages.md](packages.md): Steps for adding packages

