D lang compilers have an option -release (or similar) which turns off
asserts, contracts, and other runtime type checking. This patch wires
that up to the b_ndebug flag.
Fixes#7082
Although only one file is passed to javac at a time, if your code has
any inter-file dependencies javac still needs to know how to find other
source files for its -implicit:class feature to work whereby it will
automatically also compile files that the given file depends on.
-implicit:class is the default, practical, behaviour of javac since
otherwise it would be necessary to declare the class dependencies
for parallel java builds to be feasible.
Passing "include_directory: include_directory('.')" to jar() causes
-souredir <path/to/top/of/java/src> to be passed to javac which then
enables your source code to have inter-file class dependencies -
assuming none of your source code is generated.
This ensures that '.' is included by default.