util: use XDG_STATE_HOME for datadir on Flatpak #3131

Job	Run time
Lint	48s
macOS 12 native [GOAL install] [GUI] [no depends]	22m 10s
ARM [GOAL install] [buster]	13m 10s
Win32	14m 47s
Win64	34m 3s
i386 Linux [GOAL install] [focal]	13m 18s
x86_64 Linux [GOAL install] [GUI] [focal] [no depends]	18m 56s
x86_64 Linux [GOAL install] [GUI] [bionic] [no depends]	16m 18s
x86_64 Linux [ASan] [LSan] [UBSan] [integer] [jammy] [no depends]	19m 33s
macOS 10.14 [GOAL deploy] [GUI] [no tests] [focal]	30m 9s
	3h 3m 12s

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