lang/rust build fails

[Robert Nestor <rnestor%mac.com@localhost>]

Ran into an interesting problem trying to build lang/rust from both -current and 2020Q1 pkgsrc.  On a NetBSD installation of 9.99.45 kernel and user land, the builds succeed.  Under 9.99.60 kernel and user land the builds fail.

The failure doesn’t give much of a clue about what’s happened.  The last lines in the build.log are:

running: /pkg_comp/work/pkg/lang/rust/work/rust-bootstrap/bin/cargo build --manifest-path /pkg_comp/work/pkg/lang/rust/work/rustc-1.42.0-src/src/bootstrap/Cargo.toml --frozen
   Compiling proc-macro2 v0.4.30

At that point there’s nothing consuming CPU time in the build and everything seems to be waiting on something to happen that never does.  I’ve left the system in that state for about 24 hours and still no progress.

Any  clues? Could this be something related to some of the recent kernel changes?
Thanks,
-bob