[gcc r16-5223] libstdc++: testsuite: Add csignal missing test for SIG_IGN

[Jonathan Wakely]

https://gcc.gnu.org/g:bc7a89048eafe81702c6ab5b8236cea028212fda

commit r16-5223-gbc7a89048eafe81702c6ab5b8236cea028212fda
Author: Xavier Bonaventura <xavibonaventura@gmail.com>
Date:   Wed Nov 5 12:28:59 2025 +0100

    libstdc++: testsuite: Add csignal missing test for SIG_IGN
    
    SIG_IGN also needs to be defined according to the C++ standard.
    This was missing in the test.
    
            * testsuite/18_support/headers/csignal/macros.cc: Check for
            SIG_IGN.
    
    Signed-off-by: Xavier Bonaventura <xavibonaventura@gmail.com>

Diff:
---
 libstdc++-v3/testsuite/18_support/headers/csignal/macros.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libstdc++-v3/testsuite/18_support/headers/csignal/macros.cc b/libstdc++-v3/testsuite/18_support/headers/csignal/macros.cc
index 6d6c8217b361..1076cbca24d5 100644
--- a/libstdc++-v3/testsuite/18_support/headers/csignal/macros.cc
+++ b/libstdc++-v3/testsuite/18_support/headers/csignal/macros.cc
@@ -37,6 +37,10 @@ namespace gnu
     #error "SIG_DFL_must_be_a_macro"
 #endif
 
+#ifndef SIG_IGN
+    #error "SIG_IGN_must_be_a_macro"
+#endif
+
 #ifndef SIGFPE
     #error "SIGFPE_must_be_a_macro"
 #endif