-NOTMUCH_DEPENDS_FLAGS=`pkg-config --cflags glib-2.0 gmime-2.4 talloc`
-NOTMUCH_CXX_DEPENDS_FLAGS=$(NOTMUCH_DEPENDS_FLAGS) `xapian-config --cxxflags`
-
-NOTMUCH_CFLAGS=$(WARN_FLAGS) -O0 -g $(NOTMUCH_DEPENDS_FLAGS)
-NOTMUCH_CXXFLAGS=$(WARN_FLAGS) -O0 -g $(NOTMUCH_CXX_DEPENDS_FLAGS)
+# Additional flags that we will append to whatever the user set.
+# These aren't intended for the user to manipulate.
+extra_cflags := $(shell pkg-config --cflags glib-2.0 gmime-2.4 talloc)
+extra_cxxflags := $(shell xapian-config --cxxflags)