DO NOT MERGE - Force self-profiler on for perf run

Author: wesleywiser

src/librustc/session/config.rs

@@ -1397,7 +1397,7 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "don't interleave execution of lints; allows benchmarking individual lints"),
     crate_attr: Vec<String> = (Vec::new(), parse_string_push, [TRACKED],
         "inject the given attribute in the crate"),
-    self_profile: bool = (false, parse_bool, [UNTRACKED],
+    self_profile: bool = (true, parse_bool, [UNTRACKED],
         "run the self profiler and output the raw event data"),
     emit_stack_sizes: bool = (false, parse_bool, [UNTRACKED],
         "emits a section containing stack size metadata"),

src/librustc/util/profiling.rs

@@ -187,7 +187,12 @@ impl SelfProfiler {
         let filename =
             format!("{}.profile_events.json", opts.crate_name.clone().unwrap_or_default());
 
-        let mut file = BufWriter::new(fs::File::create(filename).unwrap());
+        let mut file =
+            if let Ok(file) = fs::File::create(filename) {
+                BufWriter::new(file)
+            } else {
+                return;
+            };
 
         let threads: Vec<_> =
             self.events