tests: Use TEST_CLIENT for test client modules
We abused SIMPLE_CLIENT_LIBS before, but if you disable simple clients,
the test suite fails to link. Use test client specific variables instead.
https://bugs.freedesktop.org/show_bug.cgi?id=71530
diff --git a/configure.ac b/configure.ac
index 41ce9ad..3d966d7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -266,6 +266,8 @@
PKG_CHECK_MODULES(CAIRO, [cairo])
+PKG_CHECK_MODULES(TEST_CLIENT, [wayland-client])
+
AC_ARG_ENABLE(simple-clients,
AS_HELP_STRING([--disable-simple-clients],
[do not build the simple wl_shm clients]),,