* doc/install.texi (Options specification): Document --with-specs.

From-SVN: r174598

gcc/ChangeLog

+2011-06-03  Nathan Sidwell  <nathan@codesourcery.com>
+
+	* doc/install.texi (Options specification): Document --with-specs.
+
 2011-06-02  Ramana Radhakrishnan  <ramana.radhakrishnan@linaro.org>
 
 	* config/arm/neon.md (orndi3_neon): Actually split it.

gcc/doc/install.texi

@@ -771,6 +771,19 @@ the installation directory for G++ header files.  The default depends
 on other configuration options, and differs between cross and native
 configurations.
 
+@item --with-specs=@var{specs}
+Specify additional command line driver SPECS.
+This can be useful if you need to turn on a non-standard feature by
+default without modifying the compiler's source code, for instance
+@option{--with-specs=%@{!fcommon:%@{!fno-common:-fno-common@}@}}.
+@ifnothtml
+@xref{Spec Files,, Specifying subprocesses and the switches to pass to them,
+gcc, Using the GNU Compiler Collection (GCC)},
+@end ifnothtml
+@ifhtml
+See ``Spec Files'' in the main manual
+@end ifhtml
+
 @end table
 
 @item --program-prefix=@var{prefix}