configure.ac: fix audio detection on OSX

[Austin English]

Fixes http://bugs.winehq.org/show_bug.cgi?id=27874

-- 
-Austin
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diff --git a/configure.ac b/configure.ac
index b213923..306a673 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1640,7 +1640,7 @@ test "x$ac_cv_member_oss_sysinfo_numaudioengines" = xyes || enable_wineoss_drv=$
 test "$ac_cv_header_linux_joystick_h" = "yes" || enable_winejoystick_drv=${enable_winejoystick_drv:-no}
 
 dnl **** Check for any sound system ****
-if test "x$ALSALIBS$COREAUDIOLIBS" = "x" -a \
+if test "x$ALSALIBS$COREAUDIO" = "x" -a \
         "x$ac_cv_member_oss_sysinfo_numaudioengines" != xyes -a \
         "x$with_alsa$with_coreaudio$with_oss" != xnonono
 then