Add subdir-objects to automake options.

configure.ac

@@ -19,7 +19,7 @@ AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_SRCDIR([cgminer.c])
 AC_CONFIG_HEADERS([config.h])
 
-AM_INIT_AUTOMAKE([foreign])
+AM_INIT_AUTOMAKE([foreign subdir-objects])
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 AC_USE_SYSTEM_EXTENSIONS