binary file is corrupted when compiled with ldc2

binary file "vitis" is inoperative when builded with ldc2/make with default options.

cause: both "amaltea" and "vitis" are builded to be dynamically linked, but the switch "-link-defaultlib-shared" is not used by build scripts of "vitis".

in consequence, "vitis" uses static runtime, but amaltea not.

suggested correction: use "-link-defaultlib-shared" switch when building "vitis"