Rollup merge of #55306 - pnkfelix:issue-54478-regression-test-jemalloc-ctl, r=nikomatsakis
Rollup merge of #55306 - pnkfelix:issue-54478-regression-test-jemalloc-ctl, r=nikomatsakis

Regression test for #54478.

This is a regression test for #54478.

I confirmed that it fails on:
rustdoc 1.30.0-beta.12 (96a229824 2018-10-04)
and passes on:
rustdoc 1.31.0-nightly (f99911a4a 2018-10-23)

Fix #54478

GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust