Check large enough

Makefile

@@ -11,6 +11,8 @@ INSTALLER_URL = https://web.archive.org/web/20070611110850fw_/http://nesa1.uni-s
 
 download_setup_exe: ## Downloads installer if missing
 	@[ -f CASAnova_Setup.exe ] || { echo "${green}Downloading CASAnova_Setup.exe...${no_color}"; wget "$(INSTALLER_URL)" -O CASAnova_Setup.exe; }
+	@[ -f CASAnova_Setup.exe ] && [ $$(stat -c%s CASAnova_Setup.exe) -gt 1000000 ] \
+		|| { echo "${red}CASAnova_Setup.exe missing or too small (download failed?)${no_color}"; exit 1; }
 
 build: download_setup_exe ## Build the Docker image (downloads installer if missing).
 	@echo "${green}Building image...${no_color}"