-AM_CPPFLAGS = -I$(top_srcdir)/include -I$(top_srcdir)/liblttng-ust-comm -I$(top_builddir)/include
-AM_CFLAGS = -fno-strict-aliasing
+AM_CPPFLAGS += -I$(top_srcdir)/liblttng-ust-comm
+AM_CFLAGS += -fno-strict-aliasing
lib_LTLIBRARIES = liblttng-ust-ctl.la