This should be more reliable (not building with `cfg(miri)` and more
accurately knowing whether a target supports std).
Known targets affected by this change:
- cygwin: should now build since it only breaks in `cfg(miri)`
- i686-pc-nto-qnx700: officially doesn't support std
closes#4
This is necessary for AVR and AMDGPU. We currently just hardcode some
flags in the binary, which is good enough. There's a new column which
keeps track of the used flags and shows them for a build.
A migration makes sure that the older results are properly backfilled
with the flags to make them build.
