Something

install: all
        for x in $(APPS); do $(INSTALL) -m 755 $$x $(DESTDIR)$(MODULES_DIR) ; done
        rm -f $(DESTDIR)$(MODULES_DIR)/app_datetime.so
        rm -f $(DESTDIR)$(MODULES_DIR)/app_qcall.so

+app_rxfax.so : app_rxfax.o
+       $(CC) $(SOLINK) -o $@ $< -lspandsp -ltiff

+app_txfax.so : app_txfax.o
+        $(CC) $(SOLINK) -o $@ $< -lspandsp -ltiff


APPS+=$(shell if [ -f $(CROSS_COMPILE_TARGET)/usr/include/osp/osp.h ]; then echo "app_osplookup.so" ; fi)

+APPS+=$(shell if [ -f /usr/include/spandsp.h ]; then echo "app_rxfax.so app_txfax.so" ; fi)
+APPS+=$(shell if [ -f /usr/local/include/spandsp.h ]; then echo "app_rxfax.so app_txfax.so" ; fi)