[epiphany] build: Switch to AM_DISTCHECK_CONFIGURE_FLAGS

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 675638db45606e026c7f69c1c9f5d49e2d34249d
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Sat Dec 19 09:17:11 2015 -0600

    build: Switch to AM_DISTCHECK_CONFIGURE_FLAGS
    
    Apparently DISTCHECK_CONFIGURE_FLAGS is for users
    
    https://www.gnu.org/software/automake/manual/html_node/Checking-the-Distribution.html

 Makefile.am |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 46dca29..2339402 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -4,7 +4,7 @@ if ENABLE_TESTS
 SUBDIRS += tests
 endif
 
-DISTCHECK_CONFIGURE_FLAGS = \
+AM_DISTCHECK_CONFIGURE_FLAGS = \
        --enable-debug
 
 @CODE_COVERAGE_RULES@