Makefile.am: Add missing line continuation lost in a rebase.

Signed-off-by: Philip Tricca <flihp@twobit.us>
diff --git a/Makefile.am b/Makefile.am
index bfee60f..5bb7b45 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -41,7 +41,7 @@
     test/tcti_device \
     test/getcommands-malloc-mock_unit \
     test/CommonPreparePrologue_unit \
-    test/GetNumHandles_unit
+    test/GetNumHandles_unit \
     test/CopyCommandHeader_unit
 TESTS = $(check_PROGRAMS)
 CLEANFILES = $(nodist_pkgconfig_DATA)