I already build a new cross-compiling environment with GTK+3.22. Once in a while, about a year, I have to rebuild the environment anyhow to use bugfixes etc.
The packages I use yet:
atk 2.16.0
cairo-fc 1.14.2
cairo-ft 1.14.2
cairo-gobject 1.14.2
cairo-pdf 1.14.2
cairo-png 1.14.2
cairo-ps 1.14.2
cairo-script 1.14.2
cairo-svg 1.14.2
cairo-tee 1.14.2
cairo-win32-font 1.14.2
cairo-win32 1.14.2
cairo 1.14.2
epoxy 1.3.1
fontconfig 2.10.92
freetype2 16.1.10
gail-3.0 3.22.15
gail 2.24.31
gdk-2.0 2.24.31
gdk-3.0 3.22.15
gdk-pixbuf-2.0 2.36.4
gdk-win32-2.0 2.24.31
gdk-win32-3.0 3.22.15
gio-2.0 2.52.2
gio-windows-2.0 2.52.2
glib-2.0 2.52.2
gmodule-2.0 2.52.2
gmodule-export-2.0 2.52.2
gmodule-no-export-2.0 2.52.2
gobject-2.0 2.52.2
gsl 1.14
gthread-2.0 2.52.2
gtk+-2.0 2.24.31
gtk+-3.0 3.22.15
gtk+-win32-2.0 2.24.31
gtk+-win32-3.0 3.22.15
gtksourceview-3.0 3.24.4
harfbuzz-icu 1.0.6
harfbuzz 1.0.6
icu-i18n 56.1
icu-io 56.1
icu-le 56.1
icu-lx 56.1
icu-uc 56.1
libecpg 9.6.5
libecpg_compat 9.6.5
libglade-2.0 2.6.4
libpgtypes 9.6.5
libpng 1.6.19
libpng16 1.6.19
libpq 9.6.5
libxml-2.0 2.9.0
pango 1.38.1
pangocairo 1.38.1
pangoft2 1.38.1
pangowin32 1.38.1
pixman-1 0.30.0
spread-sheet-widget 0.2
zlib 1.2.8
adwaita-icon-theme 3.26.0
Have fun.