HADOOP-18729. Fix mvnsite on Windows 10 (#5618)

hadoop-common-project/hadoop-common/pom.xml

@@ -652,9 +652,10 @@
                     <goal>exec</goal>
                 </goals>
                 <configuration>
-                    <executable>${basedir}/../../dev-support/bin/shelldocs</executable>
+                    <executable>${shell-executable}</executable>
                     <workingDirectory>src/site/markdown</workingDirectory>
                     <arguments>
+                        <argument>${basedir}/../../dev-support/bin/shelldocs</argument>
                         <argument>--skipprnorep</argument>
                         <argument>--output</argument>
                         <argument>${basedir}/src/site/markdown/UnixShellAPI.md</argument>