[master] e57b17288 build: limit umem to solaris

[Nils Goroll]

commit e57b17288ca87e7cd6a28d160be207bda7c7096d
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Thu Feb 6 20:21:55 2025 +0100

    build: limit umem to solaris
    
    Fixes #4192

diff --git a/configure.ac b/configure.ac
index 3f7b25257..8e683eb02 100644
--- a/configure.ac
+++ b/configure.ac
@@ -100,7 +100,11 @@ _VARNISH_CHECK_LIB(nsl, getaddrinfo)
 AC_SUBST(NET_LIBS, "${SOCKET_LIBS} ${NSL_LIBS}")
 
 # Userland slab allocator from Solaris, ported to other systems
-AC_CHECK_HEADERS([umem.h])
+case $target in
+*-*-solaris*)
+	AC_CHECK_HEADERS([umem.h])
+	;;
+esac
 
 # More portable vmb.h
 AC_CHECK_HEADERS([stdatomic.h])