build: add gtest, gmock to configure_ac

Search for gtest and gmock through configure_ac so
that their presence is required before usage.

Change-Id: I719e2d2474b148402b33c9af97075f42b4cc0afe
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/test/Makefile.am b/test/Makefile.am
index 20ddf2f..4e99de1 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -1,15 +1,12 @@
 AM_CPPFLAGS = \
-    -I$(top_srcdir) \
-    $(PTHREAD_CPPFLAGS)
+    -I$(top_srcdir)
 
 AM_CFLAGS = \
-    $(PTHREAD_CFLAGS) \
     $(SDBUSPLUS_CFLAGS) \
     $(PHOSPHOR_DBUS_INTERFACES_CFLAGS) \
     $(PHOSPHOR_LOGGING_CFLAGS)
 
-AM_CXXFLAGS = \
-    $(PTHREAD_CXXFLAGS)
+AM_CXXFLAGS =
 
 AM_LDFLAGS = \
     -lstdc++fs \
@@ -17,7 +14,8 @@
     $(PHOSPHOR_DBUS_INTERFACES_LIBS) \
     $(PHOSPHOR_LOGGING_LIBS) \
     $(OPENSSL_LIBS) \
-    -lgtest -lgtest_main -lgmock $(PTHREAD_CFLAGS) $(OESDK_TESTCASE_FLAGS)
+    $(GTEST_LIBS) $(GMOCK_LIBS) -lgmock_main
+    $(OESDK_TESTCASE_FLAGS)
 
 check_PROGRAMS =