configure: replace --enable-use_json by --enable-use-json

For consistency, use hyphen and not a mix of underscore and hyphen

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I106e03b1e00f5b610ea4403b04533e63e8d39485
diff --git a/configure.ac b/configure.ac
index f871477..f375ccf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -76,8 +76,8 @@
 AC_DEFINE_UNQUOTED([CLASS_VERSION], [$CLASS_VERSION], [Class version to register with Cereal])
 
 # enable JSON configuration
-AC_ARG_ENABLE([use_json],
-    AS_HELP_STRING([--enable-use_json], [Enable JSON configuration.]))
+AC_ARG_ENABLE([use-json],
+    AS_HELP_STRING([--enable-use-json], [Enable JSON configuration.]))
 AM_CONDITIONAL([WANTS_JSON], [test "x$enable_use_json" == "xyes"])
 AS_IF([test "x$enable_use_json" == "xyes"],
     AC_DEFINE([LED_USE_JSON],[],[Enable JSON configuration.])