Explicitly initialize fields of RunActionKnobs

Summary:
- safer
- also functional style is cleaner (`eager_dep_files` field is only initialized at construction rather than initialized to `false` and modified later)

I was removing `new_style_scratch_path`, and with `Default` I accidentally missed the field.

Reviewed By: IanChilds

Differential Revision: D65611068

fbshipit-source-id: 4e8ab867f9994f266359147faaf10022592a058a

Author: stepancheg

app/buck2_server/src/ctx.rs

@@ -356,20 +356,22 @@ impl<'a> ServerCommandContext<'a> {
             .map(|opts| opts.skip_cache_write)
             .unwrap_or_default();
 
-        let mut run_action_knobs = RunActionKnobs {
+        let eager_dep_files = if let Some(build_options) = self.build_options.as_ref() {
+            build_options.eager_dep_files
+        } else {
+            false
+        };
+
+        let run_action_knobs = RunActionKnobs {
             hash_all_commands: self.base_context.daemon.hash_all_commands,
             use_network_action_output_cache: self
                 .base_context
                 .daemon
                 .use_network_action_output_cache,
             new_style_scratch_path: self.base_context.daemon.new_style_scratch_path,
-            ..Default::default()
+            eager_dep_files,
         };
 
-        if let Some(build_options) = self.build_options.as_ref() {
-            run_action_knobs.eager_dep_files = build_options.eager_dep_files;
-        }
-
         let concurrency = self
             .build_options
             .as_ref()