https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109709
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I suppose we could do something like:
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -364,7 +364,9 @@ You must have GNU make installed to build GCC@.
Necessary (only on some platforms) to untar the source code. Many
systems' @command{tar} programs will also work, only try GNU
-@command{tar} if you have problems.
+@command{tar} if you have problems. N.B. a @command{tar} program of some
+kind is always needed to build GCC, the GNU tar requirement is only
+for extracting the sources.
@item Perl version between 5.6.1 and 5.6.24
