interpreter: handle multiple dirs in install_emptydir #14491

Job	Run time
Arch / PyPy	19m 4s
Arch Linux	16m 18s
CUDA (on Arch)	5m 45s
Fedora	20m 36s
Ubuntu Rolling (gcc, g++)	15m 39s
OpenSUSE	15m 2s
Ubuntu Rolling (--unity=on -Ddefault_library=static, --no-unittests, gcc, g++)	10m 51s
Ubuntu Bionic	14m 2s
Ubuntu Rolling (-Ddefault_library=both, --no-unittests, gcc, g++)	11m 18s
Ubuntu Rolling (clang, clang++)	18m 44s
Ubuntu Rolling (--unity=on, --no-unittests, clang, clang++)	12m 32s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, 0, gcc, g++)	10m 36s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, --unity=on, gcc, g++)	10m 59s
	3h 1m 26s

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