Check whether libcurl links to executables

Author: Matthias Koeppe

build/pkgs/curl/spkg-configure.m4

@@ -8,4 +8,19 @@ SAGE_SPKG_CONFIGURE([curl], [
     ])
     AS_IF([test -z "$ac_cv_path_CURL"], [sage_spkg_install_curl=yes])
     LIBCURL_CHECK_CONFIG(, 7.22, , [sage_spkg_install_curl=yes])
+    # Anaconda on macOS provides a libcurl with @rpath. Check that
+    # linking produces a binary than can be run. (#27941)
+    AC_CACHE_CHECK([whether programs linking to libcurl can be executed],
+      [sage_libcurl_cv_lib_curl_executable],
+      [
+           _libcurl_save_cppflags=$CPPFLAGS
+           CPPFLAGS="$LIBCURL_CPPFLAGS $CPPFLAGS"
+           _libcurl_save_libs=$LIBS
+           LIBS="$LIBCURL $LIBS"
+
+           AC_RUN_IFELSE([AC_LANG_PROGRAM([[#include <curl/curl.h>]],[[
+             curl_easy_setopt(NULL,CURLOPT_URL,NULL);
+           ]])], sage_libcurl_cv_lib_curl_executable=yes, sage_libcurl_cv_lib_curl_executable=no)
+      ])
+    AS_IF([test "$sage_libcurl_cv_lib_curl_executable" = "no"], [sage_spkg_install_curl=yes])
 ])