[LIVY-610][BUILD] optimization for windows environment build.

## What changes were proposed in this pull request?

we can remove requireOS restriction for windows building, and add execute permission for bin/livy-server.
https://issues.apache.org/jira/browse/LIVY-610
## How was this patch tested?
 tested manually.

Author: dockerzhang(张超) <[email protected]>
Author: dockerzhang <[email protected]>

Closes apache#184 from dockerzhang/windows-build.

Author: dockerzhang

assembly/assembly.xml

@@ -29,6 +29,7 @@
       <includes>
         <include>*</include>
       </includes>
+      <fileMode>0755</fileMode>
     </fileSet>
     <fileSet>
       <directory>${project.parent.basedir}</directory>

pom.xml

@@ -797,9 +797,6 @@
             <requireMavenVersion>
               <version>[3.0.0,)</version>
             </requireMavenVersion>
-            <requireOS>
-              <family>unix</family>
-            </requireOS>
           </rules>
         </configuration>
         <executions>