Add -e exe option to test8 #2565

Job	Run time
linux-x86_64	1m 32s
linux-x86_64-autotools	1m 29s
linux (i386, i686, i686-linux-gnu, i386-linux-gnu)	1m 29s
macos-x86_64	58s
macos-x86_64_autotools	1m 16s
linux (armhf, armhf, arm-linux-gnueabihf, arm-linux-gnueabihf)	1m 12s
mingw (mingw64, x86_64)	3m 35s
linux (arm64, aarch64, aarch64-linux-gnu, aarch64-linux-gnu)	1m 18s
mingw (ucrt64, ucrt-x86_64)	3m 35s
msvc (x86, Win32)	2m 4s
msvc (x64, x64)	1m 32s
mingw (clang64, clang-x86_64)	2m 38s
	22m 38s

Provide feedback