chore: improve release build options

[ThomasFrans]

closes #1192

[ThomasFrans]

I also added the codegen-units options which doesn't change anything except for code quality of the release builds (similar to lto). I added an optimized profile for testing performance as it has the same speed as the release profile, but takes way less time to compile. Neither of these options should change any behavior or debugging info.

[hrkfdn]

Merged, thanks!

[juippis]

I noticed the buildtime for 0.13.4 has tripled compared to 0.13.3. If I revert this commit, it goes back to "normal".

Not a big deal as ncspot doesn't take too long to build anyway, just typing what I observed and if someone else sees the same :)

EDIT: I see this was discussed in #1192 already.

[ThomasFrans]

I hoped that most people would get release binaries from their package managers so they wouldn't notice this change. Other people can either choose the longer compilation time or compile with the 'optimized' profile, which results in the old behavior.