[gcc r16-5540] libstdc++: Mark new istream::ignore overload always_inline

[Jonathan Wakely]

https://gcc.gnu.org/g:36c60061d6c4866585f53f45da6766793887da36

commit r16-5540-g36c60061d6c4866585f53f45da6766793887da36
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Nov 24 10:07:03 2025 +0000

    libstdc++: Mark new istream::ignore overload always_inline
    
    This means we don't need to add the new member to the explicit
    instantiation definition.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/istream (istream::ignore(streamsize, char)): Add
            always_inline attribute.

Diff:
---
 libstdc++-v3/include/std/istream | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libstdc++-v3/include/std/istream b/libstdc++-v3/include/std/istream
index 285c41cf02ba..ea232a71f5a8 100644
--- a/libstdc++-v3/include/std/istream
+++ b/libstdc++-v3/include/std/istream
@@ -556,6 +556,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       ignore();
 
 #if __cplusplus > 202302L
+      [[__gnu__::__always_inline__]]
       __istream_type&
       ignore(streamsize __n, char __delim) requires same_as<_CharT, char>
       { return ignore(__n, traits_type::to_int_type(__delim)); }