This worked (after doing "sudo gem install -V fpm" as the -N option in "gem install -V fpm -N" wasn't recognized):
sudo scripts/build.py setup-schroot-trusty

But this failed immediately:
scripts/build.py trusty-amd64

Output:
gcc (Ubuntu 4.8.4-2ubuntu1~14.04) 4.8.4
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

sh: 1: /home/pp/git/wkhtmltopdf/static-build/../qt/configure: not found
/home/pp/git/wkhtmltopdf/static-build/../qt/configure -opensource -confirm-license -fast -release -static -graphicssystem raster -webkit -exceptions -xmlpatterns -system-zlib -system-libpng -system-libjpeg -no-libmng -no-libtiff -no-accessibility -no-stl -no-qt3support -no-phonon -no-phonon-backend -no-opengl -no-declarative -no-script -no-scripttools -no-sql-ibase -no-sql-mysql -no-sql-odbc -no-sql-psql -no-sql-sqlite -no-sql-sqlite2 -no-mmx -no-3dnow -no-sse -no-sse2 -no-multimedia -nomake demos -nomake docs -nomake examples -nomake tools -nomake tests -nomake translations -silent -xrender -largefile -iconv -openssl -no-javascript-jit -no-rpath -no-dbus -no-nis -no-cups -no-pch -no-gtkstyle -no-nas-sound -no-sm -no-xshape -no-xinerama -no-xcursor -no-xfixes -no-xrandr -no-mitshm -no-xinput -no-xkb -no-glib -no-gstreamer -no-icu -no-openvg -no-xsync -no-audio-backend -no-sse3 -no-ssse3 -no-sse4.1 -no-sse4.2 -no-avx -no-neon --prefix=/home/pp/git/wkhtmltopdf/static-build/trusty-amd64/qt
command failed: exit code 32512
command inside chroot failed: exit code 256