Add fixupPhase flag to fix the cmake copy issue

[Thieso]

Fixes #391

But does this break anythink else? Is this a good fix?

[wentasah]

I think this should not break anything. Packages from this overlay are built with moveLib64 hook enabled so lib64 should always be a symlink to lib. buildEnv just creates one more level of symlinks, which should be fine.

The only downside I can see is that this approach may consume more i-nodes for symlinks than necessary. Creating one symlink from ...ros-env/lib64 to lib should be sufficient, but this creates full tree of new symlinks. But I don't think it's a problem for anybody.

[hacker1024]

I'm a little concerned about potential performance impacts here. buildEnv is already quite slow, especially on devices with low-end storage.

[Thieso]

Fair, so would there be an easier way to achieve this? Maybe force overwriting of redundant files?

[wentasah]

I tried quick&dirty way of building all humble packages and only two of those, which build successfully, contain lib64. Namely foonathan-memory-vendor and google-benchmark-vendor. They together contain 23 entries in lib64, so the overhead created by buildEnv symlinks will be negligible.

Edit: With rolling, the situation is exactly the same.

[Thieso]

Would be great if this could be merged :) Thanks