Allow setting build_by_default to False when install is True #17130

Job	Run time
Arch Linux	18m 59s
CUDA (on Arch)	7m 23s
Fedora	16m 42s
Gentoo	20m 32s
Arch / PyPy	19m 56s
OpenSUSE	14m 51s
Ubuntu Rolling (gcc, g++)	18m 11s
Ubuntu Bionic	13m 38s
Ubuntu Rolling (--unity=on -Ddefault_library=static, --no-unittests, gcc, g++)	12m 59s
Ubuntu Rolling (-Ddefault_library=both, --no-unittests, gcc, g++)	13m 18s
Ubuntu Rolling (clang, clang++)	20m 57s
Ubuntu Rolling (--unity=on, --no-unittests, clang, clang++)	14m 37s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, 0, gcc, g++)	13m 3s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, --unity=on, gcc, g++)	13m 14s
	3h 38m 20s

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