build: Add -flto to CXXFLAGS

Add -flto to CXXFLAGS to allow build optimization.

Change-Id: Id840a1bc41c8975d1bf3e64e06c4c470b8a6db2d
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/Makefile.am b/Makefile.am
index a0c64c6..9a7a000 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -35,7 +35,8 @@
 libswampd_la_CXXFLAGS = \
 	$(SDBUSPLUS_CFLAGS) \
 	$(PHOSPHOR_DBUS_INTERFACES_CFLAGS) \
-	$(PHOSPHOR_LOGGING_CFLAGS)
+	$(PHOSPHOR_LOGGING_CFLAGS) \
+	-flto
 
 libswampd_la_SOURCES = \
 	notimpl/readonly.cpp \
@@ -81,6 +82,7 @@
                             -version-info 0:0:0 -shared
 libmanualcmds_la_CXXFLAGS = $(SYSTEMD_CFLAGS) \
                              $(PHOSPHOR_DBUS_INTERFACES_CFLAGS) \
-                             $(PHOSPHOR_LOGGING_CFLAGS)
+                             $(PHOSPHOR_LOGGING_CFLAGS) \
+			     -flto
 
 SUBDIRS = . test