Fails to build with latest rustc

[RalfJung]

The latest release of compiletest_rs fails to build with the latest rustc (commit 1d8b6ce89e0874b5e93c9e41bfdd565c56372bb0):

error[E0063]: missing field `force_run_in_process` in initializer of `test::TestOpts`
   --> C:\Users\appveyor\.cargo\registry\src\github.1485827954.workers.dev-1ecc6299db9ec823\compiletest_rs-0.3.25\src\lib.rs:110:5
    |
110 |     test::TestOpts {
    |     ^^^^^^^^^^^^^^ missing `force_run_in_process`
error: aborting due to previous error