From c879554b7db4f2daf36bfccdc31ff66d8ac775da Mon Sep 17 00:00:00 2001
From: Viktor Szakats <commit@vsz.me>
Date: Sun, 14 Jul 2024 21:49:35 +0200
Subject: [PATCH] configure: limit `__builtin_available` test to Darwin

This feature test always fails on non-Apple systems. (For Apple targets
it's supported by llvm and Apple clang.)

Syncs behaviour with CMake.

Follow-up to cfd6f43d6ca7e57670b422bab7bbf10221a2cf3e #14127
Cherry-picked from #14097
Closes #14196
---
 configure.ac | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index fb7e178a79..1e18b8156e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -597,7 +597,11 @@ CURL_CHECK_WIN32_LARGEFILE
 CURL_CHECK_WIN32_CRYPTO
 
 CURL_DARWIN_CFLAGS
-CURL_SUPPORTS_BUILTIN_AVAILABLE
+case $host_os in
+  darwin*)
+    CURL_SUPPORTS_BUILTIN_AVAILABLE
+    ;;
+esac
 
 AM_CONDITIONAL([HAVE_WINDRES],
   [test "$curl_cv_native_windows" = "yes" && test -n "${RC}"])