Save the make definitions specified on the make command-line (or inferred
from the absence of command-line arguments) to the src/build/localdefs.mk file. This insures that incremental builds (e.g. in src/sbbs3) use the same build type (e.g. debug vs. release) as the intitial install. Unfortuantely it also means that switching the build type later requires editing or deleting the localdefs.mk file, which means new instructions for the wiki.