"function from *.gcda cannot be found in the *.gcno"

[asomers]

"cargo cov report" intermittently fails on FreeBSD. Occasionally it will pass, but it usually fails with the following error:

error: Cannot create graph
caused by: function from *.gcda cannot be found in the *.gcno (checksum: 3098011194, ident: 0)
caused by: parsing file /usr/home/somers/src/rust/divbuf/target/cov/build/gcda/cb17d0702a5154da.lib.gcda
caused by: parsing record index #0

Passing "-j1" to the test command, as in "cargo cov test -j1" greatly increases the pass rate. I've observed this problem on rust 1.20.0 and 1.21.1.