Created attachment 412504 [details] dev-python:PyQt5-5.5:20150921-052840.log.xz It should probably not run naked g++ there.
Created attachment 417410 [details] dev-python:PyQt5-5.5:20150921-052840.log uncompressed build log for easier viewing in the browser
Created attachment 436584 [details, diff] PyQt5-respect.patch Patch to respect *FLAGS etc, but as Davide pointed out there is the bigger problem that qtdetail is then executed.
As of 5.15.5_pre2107091435, I switched PyQt5 to a new build system based on sip-build and PyQt-builder, so this should no longer be an issue. AFAICS the new build system does not compile (or run) native binaries during the configuration process.