Makefile: Overwrite symlinks in install and install-debug

Without this, it's not possible to run the install or install-debug
rules multiple times.

Signed-off-by: Trygve Aaberge <trygveaa@gmail.com>

Makefile

@@ -232,15 +232,15 @@ install-headers: $(PUBLIC_HEADERS)
 install-debug: debug install-headers
 	test -d $(DESTDIR)$(PREFIX)/lib || $(call mkdir,$(DESTDIR)$(PREFIX)/lib)
 	install -Dm755 $(DEBUG_TARGET) $(DESTDIR)$(PREFIX)/lib/libolm_debug.$(SO).$(VERSION)
-	ln -s libolm_debug.$(SO).$(VERSION) $(DESTDIR)$(PREFIX)/lib/libolm_debug.$(SO).$(MAJOR)
-	ln -s libolm_debug.$(SO).$(VERSION) $(DESTDIR)$(PREFIX)/lib/libolm_debug.$(SO)
+	ln -sf libolm_debug.$(SO).$(VERSION) $(DESTDIR)$(PREFIX)/lib/libolm_debug.$(SO).$(MAJOR)
+	ln -sf libolm_debug.$(SO).$(VERSION) $(DESTDIR)$(PREFIX)/lib/libolm_debug.$(SO)
 .PHONY: install-debug
 
 install: lib install-headers
 	test -d $(DESTDIR)$(PREFIX)/lib || $(call mkdir,$(DESTDIR)$(PREFIX)/lib)
 	install -Dm755 $(RELEASE_TARGET) $(DESTDIR)$(PREFIX)/lib/libolm.$(SO).$(VERSION)
-	ln -s libolm.$(SO).$(VERSION) $(DESTDIR)$(PREFIX)/lib/libolm.$(SO).$(MAJOR)
-	ln -s libolm.$(SO).$(VERSION) $(DESTDIR)$(PREFIX)/lib/libolm.$(SO)
+	ln -sf libolm.$(SO).$(VERSION) $(DESTDIR)$(PREFIX)/lib/libolm.$(SO).$(MAJOR)
+	ln -sf libolm.$(SO).$(VERSION) $(DESTDIR)$(PREFIX)/lib/libolm.$(SO)
 .PHONY: install
 
 clean:;