support x fmt for sub and outside of rust directories

Signed-off-by: ozkanonur <work@onurozkan.dev>

Author: onur-ozkan

Diff for: src/bootstrap/format.rs

@@ -218,7 +218,7 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
                     WalkBuilder::new(first)
                 }
             } else {
-                WalkBuilder::new(first)
+                WalkBuilder::new(src.join(first))
             };
 
             for path in &paths[1..] {
@@ -229,7 +229,7 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
                         walker.add(path);
                     }
                 } else {
-                    walker.add(path);
+                    walker.add(src.join(path));
                 }
             }