Composite image information missing from resource-db.json when doing a compile --clean

[gnikolaidis]

While discussing https://github.com/qooxdoo/qooxdoo-compiler/issues/25, I stumbled upon what I believe is a bug of the compiler: the first time I build the project with --clean, composite image information is missing from resource-db.json (namely the "composite", "x" and "y" resource metadata keys). Invoking the compiler a second time, without --clean, makes them reappear.

# start with a clean build
> qx compile --target build --clean
> grep composite compiled/build/resource-db.json
# image combining information missing from resource-db.json
# invoking the compiler a second time, without --clean this time
> qx compile --target build
> grep composite compiled/build/resource-db.json
# image combining information found in resource-db.json, and properly working at runtime

This is 100% reproducible; the qx/decoration/... split PNGs of the stock themes also display the same problem.

[rad-pat]

We're bumping into this too.