[gcc r12-6205] Register --sysroot in the driver switches table

[Olivier Hainque <hainque@gcc.gnu.org>]

https://gcc.gnu.org/g:48e2d9b7b88dabed336cd098cd212d0e53c5125f

commit r12-6205-g48e2d9b7b88dabed336cd098cd212d0e53c5125f
Author: Olivier Hainque <hainque@adacore.com>
Date:   Mon Dec 20 17:47:24 2021 +0000

    Register --sysroot in the driver switches table
    
    This change adjusts the processing of --sysroot to save the option in the
    internal "switches" array, which lets self-specs test for it and provide a
    default value possibly dependent on environment variables, as in
    
      --with-specs=%{!-sysroot*:--sysroot=%:getenv("WIND_BASE" /target)}
    
    2021-12-20  Olivier Hainque  <hainque@adacore.com>
    
    gcc/
            * gcc.c (driver_handle_option): do_save --sysroot.

Diff:
---
 gcc/gcc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gcc/gcc.c b/gcc/gcc.c
index e5c43b0bb18..d4c8746b0aa 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -4492,7 +4492,9 @@ driver_handle_option (struct gcc_options *opts,
     case OPT__sysroot_:
       target_system_root = arg;
       target_system_root_changed = 1;
-      do_save = false;
+      /* Saving this option is useful to let self-specs decide to
+	 provide a default one.  */
+      do_save = true;
       break;
 
     case OPT_time_: