Document elf2tag script #2641

Job	Run time
linux-x86_64-autotools	1m 9s
linux-x86_64	1m 36s
macos-x86_64	56s
linux (i386, i686, i686-linux-gnu, i386-linux-gnu)	1m 25s
macos-x86_64-autotools	1m 0s
linux (armhf, armhf, arm-linux-gnueabihf, arm-linux-gnueabihf)	1m 23s
mingw (mingw64, x86_64)	3m 39s
msvc (x86, Win32)	2m 27s
linux (arm64, aarch64, aarch64-linux-gnu, aarch64-linux-gnu)	1m 26s
mingw (ucrt64, ucrt-x86_64)	4m 13s
msvc (x64, x64)	2m 22s
mingw (clang64, clang-x86_64)	2m 49s
msvc (arm64, ARM64)	2m 16s
	26m 41s

Provide feedback