8273497: building.md should link to both md and html

Backport-of: a10bb08a4c187c6c0b21cafb25877895d885427e

doc/building.html

@@ -562,7 +562,7 @@ <h4 id="general-make-control-variables">General Make Control Variables</h4>
 <li><code>CONF</code> and <code>CONF_NAME</code> - Selecting the configuration(s) to use. See <a href="#using-multiple-configurations">Using Multiple Configurations</a></li>
 </ul>
 <h4 id="test-make-control-variables">Test Make Control Variables</h4>
-<p>These make control variables only make sense when running tests. Please see <a href="testing.html">Testing the JDK</a> for details.</p>
+<p>These make control variables only make sense when running tests. Please see <strong>Testing the JDK</strong> (<a href="testing.html">html</a>, <a href="testing.md">markdown</a>) for details.</p>
 <ul>
 <li><code>TEST</code></li>
 <li><code>TEST_JOBS</code></li>
@@ -582,7 +582,7 @@ <h2 id="running-tests">Running Tests</h2>
 <p>The <a href="https://wiki.openjdk.java.net/display/Adoption">Adoption Group</a> provides recent builds of jtreg <a href="https://adopt-openjdk.ci.cloudbees.com/job/jtreg/lastSuccessfulBuild/artifact">here</a>. Download the latest <code>.tar.gz</code> file, unpack it, and point <code>--with-jtreg</code> to the <code>jtreg</code> directory that you just unpacked.</p>
 <p>To execute the most basic tests (tier 1), use:</p>
 <pre><code>make run-test-tier1</code></pre>
-<p>For more details on how to run tests, please see the <a href="testing.html">Testing the JDK</a> document.</p>
+<p>For more details on how to run tests, please see <strong>Testing the JDK</strong> (<a href="testing.html">html</a>, <a href="testing.md">markdown</a>).</p>
 <h2 id="cross-compiling">Cross-compiling</h2>
 <p>Cross-compiling means using one platform (the <em>build</em> platform) to generate output that can ran on another platform (the <em>target</em> platform).</p>
 <p>The typical reason for cross-compiling is that the build is performed on a more powerful desktop computer, but the resulting binaries will be able to run on a different, typically low-performing system. Most of the complications that arise when building for embedded is due to this separation of <em>build</em> and <em>target</em> systems.</p>

doc/building.md

@@ -835,7 +835,7 @@ configuration, as opposed to the "configure time" configuration.
 #### Test Make Control Variables
 
 These make control variables only make sense when running tests. Please see
-[Testing the JDK](testing.html) for details.
+**Testing the JDK** ([html](testing.html), [markdown](testing.md)) for details.
 
   * `TEST`
   * `TEST_JOBS`
@@ -873,8 +873,8 @@ To execute the most basic tests (tier 1), use:
 make run-test-tier1
 ```
 
-For more details on how to run tests, please see the [Testing
-the JDK](testing.html) document.
+For more details on how to run tests, please see **Testing the JDK**
+([html](testing.html), [markdown](testing.md)).
 
 ## Cross-compiling