Fix --disable-mpg123

platform/unix/configure.in

@@ -61,8 +61,7 @@ AC_SEARCH_LIBS([ov_open], [vorbisfile], [], AC_MSG_ERROR([Can't LÖVE without Vo
 
 AC_ARG_ENABLE([mpg123], AC_HELP_STRING([--disable-mpg123], [Disable mp3 support, for patent-free builds]), [], [enable_mpg123=yes])
 AS_IF([test "x$enable_mpg123" != xno],
-	AC_SEARCH_LIBS([mpg123_open_feed], [mpg123], [], AC_MSG_ERROR([Can't LÖVE without Mpg123])))
-AS_IF([test "x$enable_mpg123" != xno],
+	AC_SEARCH_LIBS([mpg123_open_feed], [mpg123], [], AC_MSG_ERROR([Can't LÖVE without Mpg123])),
 	AC_DEFINE([LOVE_NOMPG123], [], [Build without mpg123]))
 AS_IF([test "x$enable_mpg123" != xno],
 	AC_SEARCH_LIBS([mpg123_seek_64], [mpg123], AC_SUBST([FILE_OFFSET],[-D_FILE_OFFSET_BITS=64]), AC_SUBST([FILE_OFFSET],[])))