build support list options

lib/std/build.zig

@@ -557,7 +557,15 @@ pub const Builder = struct {
                 },
                 UserValue.Scalar => |s| return s,
             },
-            TypeId.List => panic("TODO list options to build script", .{}),
+            TypeId.List => switch (entry.value.value) {
+                UserValue.Flag => {
+                    warn("Expected -D{} to be a list, but received a boolean.\n", .{name});
+                    self.markInvalidUserInput();
+                    return null;
+                },
+                UserValue.Scalar => |s| return &[_][]const u8{s},
+                UserValue.List => |lst| return lst.toSliceConst(),
+            },
         }
     }