compiler/commands: make gitHash settable at compile-time.

[alaviss]

This is useful for building nightlies, since we will be building from a
generated source archive and git metadata is lost there.

[alaviss]

CI failure unrelated.

[timotheecour]

This is useful for building nightlies, since we will be building from a generated source archive and git metadata is lost there.

seems like the wrong way to do this; instead the function that generates the source archive should dump this information (as json, of course) so nothing is lost.

[alaviss]

seems like the wrong way to do this; instead the function that generates the source archive should dump this information (as json, of course) so nothing is lost.

How are you gonna feed it back to the compiler afterwards? :)

[Araq]

Merging it because nightlies need to be fixed ASAP.

[timotheecour]

fine, can be changed later

How are you gonna feed it back to the compiler afterwards? :)

@alaviss what I had in mind was:

by just trying both git log -n 1 --format=%H and readFile("nimdump.json") ?
(or the const version of those, although const really isn't needed in compiler/commands)