[gcc r16-5409] build: Define DISABLE_MULTILIB if --disable-multilib

[Rainer Orth]

https://gcc.gnu.org/g:a264167c1eddbbdb85b466a5fde190791b1a1ec9

commit r16-5409-ga264167c1eddbbdb85b466a5fde190791b1a1ec9
Author: Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>
Date:   Wed Nov 19 09:24:14 2025 +0100

    build: Define DISABLE_MULTILIB if --disable-multilib
    
    When building trunk on Solaris with --disable-multilib, I noticed that
    the non-default multilib wasn't rejected any longer, leading to
    unexpected link failures.  I could trace this to DISABLE_MULTILIB no
    longer being defined in multilib.h.  The problem ist that
    gcc/genmultilib has been changed in
    
    Author: Terry Guo <terry.guo@arm.com>
    Date:   Sun Jan 13 10:12:07 2013 +0000
    
        Makefile.in (s-mlib): New argument MULTILIB_REUSE.
    
    This patch factored out the code that sets disable_multilib and controls
    emission of that macro into a separate generated script (tmpmultilib3),
    but genmultilib itself continues to check $disable_multilib that isn't
    ever set there.
    
    Fixed by checking enable_multilib instead which is set from the
    corresponding genmultilib argument.  DISABLE_MULTILIB is only referenced
    in gcc/config/sol2.h, so no other port should be affected.
    
    Bootstrapped without regressions on i386-pc-solaris2.11 and
    sparc-sun-solaris2.11 and verifying that the non-default multilibs are
    now rejected again as expected.
    
    2025-11-18  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
    
            gcc:
            * genmultilib: Check $enable_multilib to define DISABLE_MULTILIB.

Diff:
---
 gcc/genmultilib | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/genmultilib b/gcc/genmultilib
index 756915a6bc45..e4e8941ea2a6 100644
--- a/gcc/genmultilib
+++ b/gcc/genmultilib
@@ -549,7 +549,7 @@ echo ""
 echo "static const char *multilib_options = \"${moptions}\";"
 
 # Finally output the disable flag if specified
-if [ "x${disable_multilib}" = xyes ]; then
+if [ "x${enable_multilib}" != xyes ]; then
   echo ""
   echo "#define DISABLE_MULTILIB  1"
 fi