Bump default dmdVer to 2.068.2

[wilzbach]

This would make the backend conversion a little easier as 2.068 and higher doesn't generate a new assert template everytime it's generated.

See also:

• convert divcoeff.c to D rebooted dlang/dmd#7714 (comment)
• convert divcoeff.c to D rebooted dlang/dmd#7714 (comment)
• https://dlang.org/changelog/2.068.0.html#fix14828-warning

[CyberShadow]

This needs to be made conditional, otherwise bootstrapping from source won't work.

[wilzbach]

Why? I thought 2.068.2 is the last C++ release?

[CyberShadow]

No. 2.068.2 already had idgen.d.

[wilzbach]

Argh sorry. I didn't know that. What do you propose then?
For now I think this would only be needed for DAutoTest, but I guess as soon as Walter starts using assert in the "betterC" backend, it will affect digger too...

[CyberShadow]

If we decide that we want to add another step to the from-source bootstrap process, then we can do that. But it needs to be an informed decision.

See my older comments on the previous iteration of that PR: dlang/dmd#6907 (comment)

[wilzbach]

I thought this has already been discussed and approved?

https://forum.dlang.org/post/zbxaviowooiaenaawmgs@forum.dlang.org

We've been through bootstrapping discussions a couple of times, so let me repeat what was decided when we made the frontend switch from C++ to D.

• Other platforms are bootstrapped by cross-compilation.
• DMD must be compilable with the latest stable/major release of dmd, ldc, and gdc.

To enforce this policy the Travis-CI test was set up.
Hopefully this original purpose of the Travis-CI hasn't been forgotten in the meantime.

• No other guarantees were negotiated.

[CyberShadow]

Ah, OK. I didn't see that discussion.

[wilzbach]

Seems like there's a new discussion going on -> dlang/dmd#8112

[CyberShadow]

This still needs to be made conditional, otherwise this change will break bootstrapping from source (which is a Digger feature), and more importantly, building DMD versions between 2.067.1 and 2.068.2 will no longer work (incl. bisecting commits in that range).

[CyberShadow]

@wilzbach Do you want to do the changes?

[wilzbach]

Ehm I think it will be a lot faster if you do the needed changes by yourself (there's a lot of code that I never seen/touched).
Also note that according to dlang/dmd#8112 the new minimal host compiler should be 2.074

[CyberShadow]

Fine by me, thanks.