[gcc r13-317] docs: document --with-zstd

[Martin Liska]

https://gcc.gnu.org/g:8fa689767a8a55c889683d178ae3a003ec689927

commit r13-317-g8fa689767a8a55c889683d178ae3a003ec689927
Author: Martin Liska <mliska@suse.cz>
Date:   Wed May 11 13:21:26 2022 +0200

    docs: document --with-zstd
    
            PR other/105527
    
    gcc/ChangeLog:
    
            * doc/install.texi: Document the configure option --with-zstd.

Diff:
---
 gcc/doc/install.texi | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 10bfceffceb..76392302653 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -2371,6 +2371,11 @@ For a native build and cross compiles that have target headers, the option's
 default is derived from glibc's behavior. When glibc clamps float_t to double,
 GCC follows and enables the option. For other cross compiles, the default is
 disabled.
+
+@item --with-zstd
+Specify prefix directory for installed zstd library.
+Equivalent to @option{--with-zstd-include=PATH/include} plus
+@option{--with-zstd-lib=PATH/lib}.
 @end table
 
 @subheading Cross-Compiler-Specific Options