82172c42f6
Defaults to the directory determined by the _SRC_TOP_ logic (if != ""), and the BSDSRCDIR. NETBSDSRCDIR has been provided for use by the various NetBSD source Makefiles to find the top of the NetBSD source tree, and isn't affected by the inheritance properties of _SRC_TOP_, nor does it have the magic BSDOBJDIR baggage that BSDSRCDIR is stuck with.