Add a newline at the end of test files #16610

Job	Run time
Arch Linux	19m 41s
CUDA (on Arch)	7m 35s
Fedora	19m 40s
Gentoo	21m 29s
OpenSUSE	15m 49s
Ubuntu Bionic	14m 45s
Arch / PyPy	19m 37s
Ubuntu Rolling (gcc, g++)	19m 21s
Ubuntu Rolling (--unity=on -Ddefault_library=static, --no-unittests, gcc, g++)	13m 19s
Ubuntu Rolling (-Ddefault_library=both, --no-unittests, gcc, g++)	13m 38s
Ubuntu Rolling (clang, clang++)	22m 17s
Ubuntu Rolling (--unity=on, --no-unittests, clang, clang++)	15m 15s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, 0, gcc, g++)	13m 40s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, --unity=on, gcc, g++)	13m 14s
	3h 49m 20s

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