Rollup merge of #93104 - dtolnay:ppbless, r=Mark-Simulacrum

Support --bless for pp-exact pretty printer tests

I ran into this while working on the stack of PRs containing #93102. `x.py test src/test/pretty --bless` previously would `fatal` instead of blessing the input files.

Tested by making a silly pretty-printer tweak and running the above command: 98823c3929ebfe796786345c5ee713f63317d9c6

src/tools/compiletest/src/runtest.rs

@@ -500,7 +500,19 @@ impl<'test> TestCx<'test> {
             expected = expected.replace(&cr, "");
         }
 
-        self.compare_source(&expected, &actual);
+        if !self.config.bless {
+            self.compare_source(&expected, &actual);
+        } else if expected != actual {
+            let filepath_buf;
+            let filepath = match &self.props.pp_exact {
+                Some(file) => {
+                    filepath_buf = self.testpaths.file.parent().unwrap().join(file);
+                    &filepath_buf
+                }
+                None => &self.testpaths.file,
+            };
+            fs::write(filepath, &actual).unwrap();
+        }
 
         // If we're only making sure that the output matches then just stop here
         if self.props.pretty_compare_only {