Rust compile deadlock.

[Mike Pumford <mpumford%mudcovered.org.uk@localhost>]

I'm seeing this a lot on my 8 core 8.0-RC1 amd64 pkg builder system:

   Compiling std_unicode v0.0.0 
(file:///pkg_comp/obj/pkgsrc/lang/rust/default/rustc-1.26.1-src/src/libstd_unicode)
   Compiling libc v0.0.0 
(file:///pkg_comp/obj/pkgsrc/lang/rust/default/rustc-1.26.1-src/src/rustc/libc_shim)
dead lock detected
error: Could not compile `std_unicode`.

Caused by:
  process didn't exit successfully: 
`/pkg_comp/obj/pkgsrc/lang/rust/default/rustc-1.26.1-src/build/bootstrap/debug/rustc 
--crate-name std_unicode libstd_unicode/lib.rs --error-format json 
--crate-type lib --emit=dep-info,link -C opt-level=2 -C 
metadata=0a0a866a3679cc24 -C extra-filename=-0a0a866a3679cc24 --out-dir 
/pkg_comp/obj/pkgsrc/lang/rust/default/rustc-1.26.1-src/build/x86_64-unknown-netbsd/stage0-std/x86_64-unknown-netbsd/release/deps 
--target x86_64-unknown-netbsd -L 
dependency=/pkg_comp/obj/pkgsrc/lang/rust/default/rustc-1.26.1-src/build/x86_64-unknown-netbsd/stage0-std/x86_64-unknown-netbsd/release/deps 
-L 
dependency=/pkg_comp/obj/pkgsrc/lang/rust/default/rustc-1.26.1-src/build/x86_64-unknown-netbsd/stage0-std/release/deps 
--extern 
core=/pkg_comp/obj/pkgsrc/lang/rust/default/rustc-1.26.1-src/build/x86_64-unknown-netbsd/stage0-std/x86_64-unknown-netbsd/release/deps/libcore-64eda9404cebac9f.rlib` 
(exit code: 1)
warning: build failed, waiting for other jobs to finish...
error: build failed

With MAKE_JOBS set to 8 a deadlock during build is happens most of the 
time. IT becomes slightly more intermittent if I mark the package as not 
MAKE_JOBS safe but I still tend to have to build rust multiple times 
until I get a working run. Is this a rust bug, or a rust netbsd runtime bug?

Mike