add cscope Make rule #281

Job	Run time
linux (tiny, clang, none)	1m 37s
linux (tiny, gcc, none)	1m 51s
linux (normal, clang, none)	8m 15s
linux (normal, gcc, none)	8m 57s
linux (huge, clang, none)	8m 1s
linux (huge, gcc, none)	14m 9s
linux (tiny, clang, nogui)	1m 22s
linux (tiny, gcc, nogui)	1m 40s
linux (huge, gcc, testgui, true, true)	22m 5s
linux (huge, clang, asan)	25m 43s
linux (huge, gcc, unittests, true)	2m 27s
linux (normal, gcc, vimtags)	1m 53s
macos (tiny)	3m 30s
macos (normal)	7m 24s
macos (huge)	13m 25s
windows (HUGE, msvc, no, no, x64)	8m 7s
windows (HUGE, mingw, yes, yes, x86, yes)	14m 12s
windows (HUGE, msvc, no, yes, x86)	10m 32s
windows (HUGE, mingw, yes, no, x64, yes)	12m 11s
windows (NORMAL, msvc, yes, no, x86)	7m 52s
windows (NORMAL, mingw, no, yes, x64)	10m 23s
windows (TINY, msvc, yes, yes, x64)	2m 33s
windows (TINY, mingw, no, no, x86)	5m 7s
	3h 13m 16s

Provide feedback