Fix ci-prepare when OTP builds exist

erlang.mk

@@ -5386,9 +5386,11 @@ endef
 $(foreach otp,$(CI_OTP),$(eval $(call ci_target,$(otp))))
 
 define ci_otp_target
+ifeq ($(wildcard $(CI_INSTALL_DIR)/$(1)),)
 $(CI_INSTALL_DIR)/$(1): $(KERL)
 	$(KERL) build git $(OTP_GIT) $(1) $(1)
 	$(KERL) install $(1) $(CI_INSTALL_DIR)/$(1)
+endif
 endef
 
 $(foreach otp,$(CI_OTP),$(eval $(call ci_otp_target,$(otp))))