purge all rustwide build directories before each build

src/docbuilder/rustwide_builder.rs

@@ -363,6 +363,19 @@ impl RustwideBuilder {
             }
         }
 
+        // FIXME: for now, purge all build dirs before each build.
+        // Currently we have some error situations where the build directory wouldn't be deleted
+        // after the build failed:
+        // https://github.com/rust-lang/docs.rs/issues/820
+        // This should be solved in a better way, likely refactoring the whole builder structure,
+        // but for now we chose this simple way to prevent that the build directory remains can
+        // fill up disk space.
+        // This also prevents having multiple builders using the same rustwide workspace,
+        // which we don't do. Currently our separate builders use a separate rustwide workspace.
+        self.workspace
+            .purge_all_build_dirs()
+            .map_err(FailureError::compat)?;
+
         let mut build_dir = self.workspace.build_dir(&format!("{name}-{version}"));
         build_dir.purge().map_err(FailureError::compat)?;