incr.comp.: Edge to Krate depnode when building regex in debug mode

[michaelwoerister]

Occurs with regex 0.1.75 (ac9ced6). The Krate-edge leads to everything being re-compiled for any change. The edge does not occur when compiling with --release.

[michaelwoerister]

Occurs when compiling with -Cdebuginfo=1 but not with -Cdebuginfo=0.

[michaelwoerister]

Does not occur in nightly-2016-11-29, so it must have been introduced recently. #37954 looks suspicious.

[michaelwoerister]

Fails with nightly-2016-12-01.

[michaelwoerister]

The regression introduced somewhere in this range: 1c44857...908dba0