'lib' holds source code for libraries used by Emacs and its utilities
'lib-src' holds the source code for some utility programs for use by or
with Emacs, like movemail and etags.
+'lwlib' holds the sources of the Lucid Widget Library used on X.
+'oldXMenu' source files from X11R2 XMenu library, used in non-toolkit builds.
'etc' holds miscellaneous architecture-independent data files Emacs
uses, like the tutorial text and tool bar images.
The contents of the 'lisp', 'leim', 'info', and 'doc'
Nextstep port of Emacs, for GNUstep and macOS Cocoa.
'nt' holds code and documentation for building Emacs on MS-Windows.
'test' holds tests for various aspects of Emacs's functionality.
+'modules' holds the modhelp.py helper script.
+'admin' holds files used by Emacs developers, and Unicode data files.
+'build-aux' holds auxiliary files used during the build.
+'m4' holds Autoconf macros used for generating the configure script.
Building Emacs on non-Posix platforms requires tools that aren't part
of the standard distribution of the OS. The platform-specific README