Using pkg-config to find this variable is nice if it works. Go back to
the previously used value if it doesn't.
extra_cxxflags := $(shell xapian-config --cxxflags)
emacs_lispdir := $(shell pkg-config emacs --variable sitepkglispdir)
+# Hard-code if this system doesn't have an emacs.pc file
+ifeq ($(emacs_lispdir),)
+ emacs_lispdir = $(prefix)/share/site-lisp
+endif
# Now smash together user's values with our extra values
override CFLAGS += $(WARN_FLAGS) $(extra_cflags)