INSTALL: add a note about GNU interactive tools has been renamed

In recent versions GNU's git has been renamed to gnuit, document this
while talking about how to resolve the conflict.
Signed-off-by: NMiklos Vajna <vmiklos@frugalware.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

INSTALL

@@ -38,6 +38,10 @@ Issues of note:
    has been actively developed since 1997, and people have moved over to
    graphical file managers.
 
+   NOTE: As of gnuit-4.9.2, the GNU interactive tools package has been
+         renamed. You can compile gnuit with the --disable-transition
+         option and then it will not conflict with git.
+
  - You can use git after building but without installing if you
    wanted to.  Various git commands need to find other git
    commands and scripts to do their work, so you would need to