Resolving with statically built Qt is very slow

Building projects with a statically built Qt resolve very slowly. More specifically, Qbs spends a lot of time resolving the build before commencing actual build if for example a `.qbs` file has been touched.

Steps to reproduce:

1. Extract attached example project
2. Point the profile in `slow.qbs` to a statically built Qt qmake.
3. Build once `qbs build profile:static-qt`
4. Time a zero-build: `time qbs build profile:static-qt`
5. Touch the `.qbs` file to trigger project resolving: `touch slow.qbs`
6. Time again: `time qbs build profile:static-qt`

Example output:

➜  slow-static-qbs qbs --version
1.14.1
➜  slow-static-qbs qbs build profile:static-qt
... (output omitted ...
➜  slow-static-qbs time qbs build profile:static-qt
Restoring build graph from disk
Building for configuration default
Build done for configuration default.
/srv/build-deps/toolchains/QtCreator/QtCreator-4.10.2/Tools/QtCreator/bin/qbs  0,09s user 0,02s system 94% cpu 0,109 total
➜  slow-static-qbs touch slow.qbs
➜  slow-static-qbs time qbs build profile:static-qt
Restoring build graph from disk
Resolving project for configuration default
Building for configuration default
Build done for configuration default.
qbs  40,63s user 0,55s system 99% cpu 41,213 total

As shown above, after simply touching the qbs file the build go from taking 0.02s to over 40s for a relatively simple project. With a dynamically linked Qt the same project will build in less than 2 seconds in both cases.