Fix the extension for the Windows packages on swift.org (#388)

Author: shahmishal

download/_build-platform.html

@@ -29,10 +29,11 @@
                 <span class="release">
 
                   {% if platform.name == "Windows 10" %}
-                  <p title="Download" download>{{ platform.name }} <sup>2</sup></p>
-                   
+                    <p title="Download" download>{{ platform.name }} <sup>2</sup></p>
+                    {% assign package_extension = 'exe' %}
                   {% else %}
-                  <p title="Download" download>{{ platform.name }}</p>
+                    <p title="Download" download>{{ platform.name }}</p>
+                    {% assign package_extension = 'tar.gz' %}
                   {% endif %}
                 </span>
             </td>
@@ -46,8 +47,8 @@
                     {% assign platform_name = platform.name | remove : ' ' | downcase %}
                 {% endif %}
                 {% assign tag_downcase = include.platform.tag | downcase %}
-                <a href="https://download.swift.org/{{ tag_downcase }}/{{ platform_name_url }}/{{ include.platform.tag}}/{{ include.platform.tag}}-{{ platform_name }}.tar.gz">{{ arch }}</a>
-                <a href="https://download.swift.org/{{ tag_downcase }}/{{ platform_name_url }}/{{ include.platform.tag}}/{{ include.platform.tag}}-{{ platform_name }}.tar.gz.sig" title="PGP Signature" class="signature">Signature ({{ arch }})</a>
+                <a href="https://download.swift.org/{{ tag_downcase }}/{{ platform_name_url }}/{{ include.platform.tag}}/{{ include.platform.tag}}-{{ platform_name }}.{{ package_extension }}">{{ arch }}</a>
+                <a href="https://download.swift.org/{{ tag_downcase }}/{{ platform_name_url }}/{{ include.platform.tag}}/{{ include.platform.tag}}-{{ platform_name }}.{{ package_extension }}.sig" title="PGP Signature" class="signature">Signature ({{ arch }})</a>
             {% endfor %}
             </td>
             <td class="docker-tag">