Building on Macs (#513)

* Building on Macs

* Add Mac building documentation

* Review

* Update for new z64compress

* Review

* git subrepo pull --force tools/ZAPD

subrepo:
  subdir:   "tools/ZAPD"
  merged:   "155a463a5"
upstream:
  origin:   "https://github.com/zeldaret/ZAPD.git"
  branch:   "master"
  commit:   "155a463a5"
git-subrepo:
  version:  "0.4.3"
  origin:   "https://github.com/ingydotnet/git-subrepo.git"
  commit:   "2f68596"

* Fix some obvious warnings

* Rewrite docs

* -;

* git subrepo pull --force tools/ZAPD

subrepo:
  subdir:   "tools/ZAPD"
  merged:   "fd5a7f434"
upstream:
  origin:   "https://github.com/zeldaret/ZAPD.git"
  branch:   "master"
  commit:   "fd5a7f434"
git-subrepo:
  version:  "0.4.3"
  origin:   "https://github.com/ingydotnet/git-subrepo.git"
  commit:   "2f68596"

Co-authored-by: Anghelo Carvajal <angheloalf95@gmail.com>

docs/BUILDING_MACOS.md

@@ -0,0 +1,83 @@
+# Building on macOS
+
+**N.B. C++17 is required to build the asset processing program that we use (ZAPD), so check your OS version can support this before proceeding**
+
+
+## Dependencies
+
+For macOS, use Homebrew to install the following dependencies:
+
+* coreutils
+* make
+* python3
+* libpng
+* bash
+* clang-format 11
+
+You can install them with the following commands:
+
+```bash
+brew update
+brew install coreutils make python3 libpng bash clang-format@11
+```
+
+(The repository expects Homebrew-installed programs to be either linked correctly in `$PATH` etc. or in their default locations.)
+
+
+## Building mips-linux-binutils
+
+The following instructions are written for MacOS users but should apply to any Unix-like system, with maybe some modifications at the end regarding the bash_profile.
+
+Create destination dir for binutils
+```bash
+sudo mkdir -p /opt/cross
+```
+
+Create and enter local working dir
+```bash
+mkdir ~/binutils-tmp
+cd ~/binutils-tmp
+```
+
+Get and extract binutils source
+```bash
+wget https://ftp.gnu.org/gnu/binutils/binutils-2.35.tar.bz2
+tar xjf binutils-2.35.tar.bz2
+```
+(You may find this command does not work: if so, just access the URL in a browser and save it to `~/binutils-tmp`.)
+
+Create and enter a build directory
+```bash
+mkdir build-binutils
+cd build-binutils
+```
+
+Configure the build
+```bash
+../binutils-2.35/configure --target=mips-linux-gnu --prefix=/opt/cross --disable-gprof --disable-gdb --disable-werror
+```
+
+Make and install binutils
+```bash
+make -j
+sudo make install
+```
+
+Edit your `~/.bash_profile`/`~/.zsh_profile` (or whichever shell you use) to add the new binutils binaries to the system PATH
+```bash
+echo "export PATH=$PATH:/opt/cross/bin" >> ~/.bash_profile
+```
+
+Reload ~/.bash_profile (or just launch a new terminal tab)
+```bash
+source ~/.bash_profile
+```
+
+If this worked, you can now delete the temporary directory `~/binutils-tmp`.
+
+
+## Final note
+
+Apple's version of `make` is very out-of-date, so you should use the brew-installed `gmake` in place of `make` in this repo from now on.
+
+You should now be able to continue from [step 2](README.md#2-clone-the-repository) of the Linux instructions.