gui/build.sh: also find qmake if it is named qmake5

As of Qt 5.15.3 Gentoo has started appending the Qt5 executables with a 5[1] in preparation of the move to Qt6 (where this behaviour is default)[2]. This patch enables the build system to find qmake if it has been appended with a 5.

Furthermore, recent changes in the way Gentoo handles Go packages means that we now require all Go dependencies to be either bundled or distributed in a single separate tarball[3]. Would it be possible to distribute such a tarball here upstream? Alternatively I can just generate one myself for each release.

[1] https://www.gentoo.org/support/news-items/2022-03-30-qt-5_15_3-bump.html [2] https://archives.gentoo.org/gentoo-dev/message/5f3681b5b28dabeb5339d44e9585d29f [3] https://devmanual.gentoo.org/eclass-reference/go-module.eclass/index.html

Signed-off-by: Andrew Ammerlaan andrewammerlaan@gentoo.org