'java' holds the Java code for the Emacs port to Android.
'cross' holds Makefiles and an additional copy of gnulib used to build
Emacs for Android devices.
+'exec' holds the source code to several helper executables used to run
+ user-installed programs on Android.
Building Emacs on non-Posix platforms requires tools that aren't part
of the standard distribution of the OS. The platform-specific README