[install.texi] Add note against GNAT 4.8 on ARM targets

	* doc/install/texi: Add note against GNAT 4.8 on ARM hosts.

From-SVN: r231500

gcc/ChangeLog

+2015-12-10  Alan Lawrence  <alan.lawrence@arm.com>
+
+	* doc/install.texi: Add note against GNAT 4.8 on ARM hosts.
+
 2015-12-10  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/68785

gcc/doc/install.texi

@@ -3484,6 +3484,10 @@ require GNU binutils 2.13 or newer.  Such subtargets include:
 @code{arm-*-netbsdelf}, @code{arm-*-*linux-*}
 and @code{arm-*-rtemseabi}.
 
+Building the Ada frontend commonly fails (an infinite loop executing
+@code{xsinfo}) if the host compiler is GNAT 4.8.  Host compilers built from the
+GNAT 4.6, 4.9 or 5 release branches are known to succeed.
+
 @html
 <hr />
 @end html