Rustdoc itself no longer requires proc macros to build

This avoids a full compiler build in order to build and/or run tests for
rustdoc.

src/bootstrap/test.rs

@@ -952,8 +952,7 @@ impl Step for Compiletest {
         if suite.ends_with("fulldeps") ||
             // FIXME: Does pretty need librustc compiled? Note that there are
             // fulldeps test suites with mode = pretty as well.
-            mode == "pretty" ||
-            mode == "rustdoc"
+            mode == "pretty"
         {
             builder.ensure(compile::Rustc { compiler, target });
         }

src/test/rustdoc/rustc-macro-crate.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // no-prefer-dynamic
+// ignore-stage1
 
 #![crate_type = "proc-macro"]