Commit 6ddc2d0 for zlib

commit 6ddc2d07ba96acf36e84169de1c1314df485a65a
Author: Mark Adler <git@madler.net>
Date:   Sun Nov 1 17:15:21 2026 -0800

    Fix configure when using zlib.map with some linkers.

    configure tests a one-function object with zlib.map, which some
    linkers (e.g. lld 17 and later) would fail for undefined symbols.
    configure would then only build the static library.

diff --git a/configure b/configure
index 61ca1c8..4a02de8 100755
--- a/configure
+++ b/configure
@@ -518,8 +518,12 @@ EOF
 if test $shared -eq 1; then
   echo Checking for shared library support... | tee -a configure.log
   # we must test in two steps (cc then ld), required at least on SunOS 4.x
+  # the second link test is for linkers like lld that by default reject a
+  # version script naming symbols that the test object doesn't define
   if try $CC -c $SFLAGS $test.c &&
-     try $LDSHARED $SFLAGS $LDFLAGS -o $test$shared_ext $test.o; then
+     { try $LDSHARED $SFLAGS $LDFLAGS -o $test$shared_ext $test.o ||
+       try $LDSHARED $SFLAGS $LDFLAGS -Wl,--undefined-version \
+           -o $test$shared_ext $test.o; }; then
     echo Building shared library $SHAREDLIBV with $CC. | tee -a configure.log
   elif test -z "$old_cc" -a -z "$old_cflags"; then
     echo No shared library support. | tee -a configure.log