gnome: Add support for gi-compile-repository for generate_gir #17301

Job	Run time
Arch / PyPy	19m 35s
Arch Linux	20m 57s
CUDA (on Arch)	7m 9s
Fedora	17m 43s
Ubuntu Rolling (gcc, g++)	18m 21s
Gentoo	22m 32s
Ubuntu Rolling (--unity=on -Ddefault_library=static, --no-unittests, gcc, g++)	12m 46s
OpenSUSE	16m 36s
Ubuntu Rolling (-Ddefault_library=both, --no-unittests, gcc, g++)	13m 18s
Ubuntu Bionic	13m 36s
Ubuntu Rolling (clang, clang++)	21m 1s
Ubuntu Rolling (--unity=on, --no-unittests, clang, clang++)	14m 39s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, 0, gcc, g++)	13m 5s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, --unity=on, gcc, g++)	14m 7s
	3h 45m 25s

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