node 10.x regression: update fs-extra dependency

[ccprog]

harp compilation no longer works with node 10.x due to an outdated version of fs-extra, which is itself dependent on graceful-fs. You get a core dump like the one reported here.

graceful-fs < v4 depends on https://github.com/addaleax/native, which is deprectated and no longer executable with node 10, see isaacs/node-graceful-fs#130.

Updating fs-extra to v7.0.0 solved the whole issue for me.

[ccprog]

Looking closer I found that terraform had a dependency on less 2.5.3; the graceful-fs dep in there is optional, so the update worked out. Nonetheless, at least less 2.7 is needed to get completely rid of graceful-fs 3 dependencies.