Enable building Emacs 27

Also embed various dylib libraries directly into the application, so
they're not required to be installed via Homebrew for the app to work.

README.md

@@ -1,63 +1,77 @@
-# build-emacs-for-osx
+# build-emacs-for-macos
 
-Use this script at your own risk. It currently works for me on my own machine,
-which as of writing is:
+Use this script at your own risk. As of writing (2020-02-02) it works for me on
+my own machine to build the `emacs-27` release branch. My machine is a late-2016
+13-inch Touchbar MacBook Pro runnning macOS 10.15.2 and Xcode 11.3.
 
-* OS X 10.8.5 (12F45)
-* Xcode 5.0 (5A1413)
+Your luck may vary.
 
-Your luck might vary. Do note that it does not build a universal application.
-The CPU architecture of the built application will be that of the machine it
-was built on.
+The build produced does have some limitations:
 
+- It is not a universal application. The CPU architecture of the built
+  application will be that of the machine it was built on.
+- The minimum required macOS version of the built application will be the same
+  as that of the machine it was built on.
 
 ## Why?
 
-I've been using [Homebrew][] the past few
-months to build from HEAD. Homebrew comes with a number of patches, including
-the [sRGB][] patches which I use.
+- To use new features available from master or pre-release branches, which have
+  not made it into a official stable release yet.
+- Homebrew builds of Emacs are not self-contained applications, making it very
+  difficult when doing HEAD builds and you need to rollback to a earlier
+  version.
+- Builds from [emacsformacosx.com](https://emacsformacosx.com/) has had no new
+  nightly builds for two months right now.
+- Both Homebrew HEAD builds, and nightly builds from emacsformacosx.com are
+  built from the `master` branch. This script allows you to choose any branch
+  you want. I am currently building from the `emacs-27` branch which is the
+  basis of the upcoming Emacs 27 release, meaning it should be more stable than
+  `master` builds.
 
-[homebrew]: http://mxcl.github.com/homebrew/
-[srgb]: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=8402
-
-Homebrew does not build a self-contained application though, which caused
-issues for me when I needed to rollback to a specific build. I found the
-easiest way to build a completely self-contained Emacs.app nightly from a
-specific date with custom patches was to do it manually.
-
-So I decided to quickly hack together a script to automate that manual
-process. The code is a horrible hack, but it (seemingly) works as I'm writing
-this in Emacs built with it.
+## Requirements
 
+- [Xcode](https://apps.apple.com/gb/app/xcode/id497799835?mt=12)
+- [Homebrew](https://brew.sh/)
+- All Homebrew formula listed in the `Brewfile`, which can all easily be
+  installed by running:
+  ```
+  brew bundle
+  ```
 
 ## Usage
 
-Myself I run the following command which will download a tarball of the
-`master` branch, apply the sRGB patch, and build Emacs.app:
+Then to download a tarball of the `master` branch, build Emacs.app:
 
-    ./build-emacs-for-osx
+    ./build-emacs-for-macos
 
-Or for example if you want to build the `emacs-24.3` tag, run:
+If you want to build the `emacs-27` git branch, run:
 
-    ./build-emacs-for-osx emacs-24.3
+    ./build-emacs-for-macos emacs-27
 
-Resulting applications are saved to the `builds` directory in a bzip2
-compressed tarball.
+If you want to build the stable `emacs-26.3` git tag, run:
 
+    ./build-emacs-for-macos emacs-26.3
+
+Resulting applications are saved to the `builds` directory in a bzip2 compressed
+tarball.
 
 ## Internals
 
-I decided to pull Emacs' source from a GitHub [mirror][repo] rather than the
-official Bzr repo cause I'm not familiar with Bzr, and GitHub lets you easily
-download tarballs of any branch, commit or tag. And the tarballs from GitHub
-are just over 30MB, compared to ~1GB to pull the offical Bzr repo.
+The script downloads the source code as a gzipped tar archive from the [GitHub
+mirror](https://github.com/emacs-mirror/emacs) repository, as it makes it very
+easy to get a tarball of any given git reference.
 
-[repo]: https://github.com/mirrors/emacs
-
-The only option passed in `./configure` is `--with-ns`, meaning the resulting
-application only supports the CPU architecture of the system is was built on.
-There might be more side-effects to, but I haven't noticed any.
+It then runs `./configure` with a various options, partly based on what [David
+Caldwell](https://github.com/caldwell)'s
+[build-emacs](https://github.com/caldwell/build-emacs) scripts do, including
+copying various dynamic libraries into the application itself. So the built
+application should in theory run on a macOS install that does not have homebrew,
+or do no have the relevant brew formula installed.
 
+Code quality, is well, non-existent. The build script started life a super-quick
+hack back in 2013, and now it's even more of a dirty hack. I might clean it up
+and add unit tests if I end up relying on this script for a prolonged period of
+time. For now I plan to use it until Emacs 27 is officially released.
 
 ## License
 
@@ -65,7 +79,7 @@ There might be more side-effects to, but I haven't noticed any.
         DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                     Version 2, December 2004
 
- Copyright (C) 2013 Jim Myhrberg
+ Copyright (C) 2020 Jim Myhrberg
 
  Everyone is permitted to copy and distribute verbatim or modified
  copies of this license document, and changing it is allowed as long