[Qt] Fix nTransactionFee in qt-settings
Gitian fixes for 0.9.0rc1 build

- Add 'g++' package (virtualbox images don't have this by default)
- Workaround for determinism in Qt5 resources
- Pass --disable-maintainer-mode --disable-dependency-tracking to
  configure for libqrencode to avoid random errors about missing m4
  directory
- Fix typo -with-pic -> --with-pic

It is not necessary to rebuild dependencies after this commit.
Fixes #3610 and #3612.
added missing homebrew qt dependency on mac osx build documentation.
Merge pull request #3620

65615a3 Gitian fixes for 0.9.0rc1 build (Wladimir J. van der Laan)
Merge pull request #3621 from gubatron/build-osx-qt-dependency-missing

added missing homebrew qt dependency on mac osx build documentation.
Merge pull request #3613 from cozz/cozz1

[Qt] Fix nTransactionFee in qt-settings