Only quote program arguments if they actually contain spaces

src/main/java/net/fabricmc/loom/configuration/ide/RunConfig.java

@@ -210,7 +210,12 @@ public class RunConfig {
 			}
 
 			first = false;
+
+			if (arg.contains(" ")) {
 				sb.append("\"").append(arg).append("\"");
+			} else {
+				sb.append(arg);
+			}
 		}
 
 		return sb.toString();

src/test/groovy/net/fabricmc/loom/test/unit/RunConfigUnitTest.groovy

@@ -33,6 +33,6 @@ class RunConfigUnitTest extends Specification {
             def args = RunConfig.joinArguments(["-Dfabric.test=123", "-Dfabric.test=abc 123"])
 
         then:
-            args == '"-Dfabric.test=123" "-Dfabric.test=abc 123"'
+            args == '-Dfabric.test=123 "-Dfabric.test=abc 123"'
     }
 }