[gcc(refs/vendors/riscv/heads/gcc-15-with-riscv-opts)] RISC-V: Remove use of structured binding to fix compiler warning

[Jeff Law]

https://gcc.gnu.org/g:62294f935f95cbd8520ab6e12bb02fabcf2c5c01

commit 62294f935f95cbd8520ab6e12bb02fabcf2c5c01
Author: Christoph Müllner <christoph.muellner@vrull.eu>
Date:   Mon Jul 28 17:31:06 2025 +0200

    RISC-V: Remove use of structured binding to fix compiler warning
    
    Function riscv_ext_is_subset () uses structured bindings to iterate over
    all keys and values of an unordered map.  However, this is only
    available since C++17 and causes a warning like this:
      warning: structured bindings only available with ‘-std=c++17’
    This patch addresses the warning.
    
    gcc/ChangeLog:
    
            * common/config/riscv/riscv-common.cc (riscv_ext_is_subset):
            Remove use of structured binding to fix compiler warning.
    
    Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>
    (cherry picked from commit b267361f23c98ab9d9ca2b0fcf23b57117a84752)

Diff:
---
 gcc/common/config/riscv/riscv-common.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/common/config/riscv/riscv-common.cc b/gcc/common/config/riscv/riscv-common.cc
index 82037a334528..da3cb9f788dc 100644
--- a/gcc/common/config/riscv/riscv-common.cc
+++ b/gcc/common/config/riscv/riscv-common.cc
@@ -1606,8 +1606,9 @@ bool
 riscv_ext_is_subset (struct cl_target_option *opts,
 		     struct cl_target_option *subset)
 {
-  for (const auto &[ext_name, ext_info] : riscv_ext_infos)
+  for (const auto &riscv_ext_info : riscv_ext_infos)
     {
+      const auto &ext_info = riscv_ext_info.second;
       if (ext_info.check_opts (opts) && !ext_info.check_opts (subset))
 	return false;
     }