mainloop: Use sdeventplus

Convert to using sdeventplus instead of sd_event directly.

Change-Id: Ie8ee25c2d75ac4c56b88fb79f70eaa53c4f7b6e4
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/Makefile.am b/Makefile.am
index c0a30ea..3d5f786 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -9,11 +9,13 @@
 libhwmon_la_LIBADD = \
 	-lstdc++fs \
 	$(SDBUSPLUS_LIBS) \
+	$(SDEVENTPLUS_LIBS) \
 	$(PHOSPHOR_DBUS_INTERFACES_LIBS) \
 	$(PHOSPHOR_LOGGING_LIBS) \
 	$(GPIOPLUS_LIBS)
 libhwmon_la_CXXFLAGS = \
 	$(SDBUSPLUS_CFLAGS) \
+	$(SDEVENTPLUS_CFLAGS) \
 	$(PHOSPHOR_DBUS_INTERFACES_CFLAGS) \
 	$(PHOSPHOR_LOGGING_CFLAGS) \
 	$(GPIOPLUS_CFLAGS)