ECM is a pure CMake macro collection. The KF5-era package had
platforms.all; restore it so non-KDE consumers like turbo-unwrapped
keep evaluating on Darwin.
A lot of things hard-require the ECM bits that use it now.
Due to some cursed interaction between Qt's use of cmake and our
strictDeps patch, this makes a bunch of builds fall over until
things are moved (or, in some cases, copied) to nativeBuildInputs.
Disabling strictDeps makes things build, but starts leaking build-deps
into the final outputs via the ecm-hook wrapper, so just ADD ALL THE THINGS
for now, and hopefully we can figure out how to do this properly later.
Those would be problematic with __structuredAttrs turned on, because
they'd turn those nice bash arrays back into strings - and potentially
lose some of the values on the way.
In `kdePackages`, `strictDeps` is set and `extra-cmake-modules` goes into
`buildInputs`. The hook should run against the `buildInputs`, so it should
have `hostOffset`. This fixes for example the loading of translations that
come from dependencies.
