configure: limit `SystemConfiguration` test to non-c-ares, IPv6 builds

The framework this check detects is necessary for the function
`SCDynamicStoreCopyProxies()` used in `lib/macos.c`. Non-c-ares,
IPv6-enabled builds touch this codepath.

Limit the feature check for builds that actually need it.

It brings this in sync with CMake which already worked this way.

Cherry-picked from #14097
Closes #14126

diff --git a/configure.ac b/configure.ac
index 0ea0c16d17854eeef0e70ae2fc9614625c61ab86..6544b6693f211e12f03b0436c3ae185e16fbf7c5 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -597,7 +597,6 @@ CURL_CHECK_WIN32_LARGEFILE
 CURL_CHECK_WIN32_CRYPTO
 
 CURL_DARWIN_CFLAGS
-CURL_DARWIN_SYSTEMCONFIGURATION
 CURL_SUPPORTS_BUILTIN_AVAILABLE
 
 AM_CONDITIONAL([HAVE_WINDRES],
@@ -3875,6 +3874,10 @@ AM_CONDITIONAL(BUILD_LIBHOSTNAME, test x$build_libhostname = xyes)
 
 if test "x$want_ares" != xyes; then
   CURL_CHECK_OPTION_THREADED_RESOLVER
+
+  if test "$ipv6" = yes; then
+    CURL_DARWIN_SYSTEMCONFIGURATION
+  fi
 fi
 
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