Install openlibm from Makefile

Makefile

@@ -36,6 +36,8 @@ install: all
 	mkdir -pv "$(DESTDIR)/include"
 	cp -rv "include"/* "$(DESTDIR)/include"
 	cp -rv "target/include"/* "$(DESTDIR)/include"
+	cp -rv "target/openlibm/include"/* "$(DESTDIR)/include"
+	cp -rv "target/openlibm/src"/*.h "$(DESTDIR)/include"
 	cp -v "$(BUILD)/debug/libc.a" "$(DESTDIR)/lib"
 	cp -v "$(BUILD)/debug/crt0.o" "$(DESTDIR)/lib"
 	cp -v "$(BUILD)/openlibm/libopenlibm.a" "$(DESTDIR)/lib/libm.a"