importing 7zip from chemistry repository

packages/7zip.xml

+<?xml version="1.0" encoding="UTF-8"?>
+
+<packages>
+
+  <package id="7zip" name="7-Zip" revision="%version%.1" reboot="false" priority="0">
+    <variable name="version" value="19.00" />
+    <variable name="fileversion" value="1900" />
+
+    <check type="uninstall" condition="exists" path="7-Zip %version% (x64)" architecture="x64"/>
+    <check type="uninstall" condition="exists" path="7-Zip %version%" architecture="x86"/>
+
+    <install cmd="%software%\7zip\7z%fileversion%-x64.exe /S" architecture="x64" />
+    <install cmd="%software%\7zip\7z%fileversion%.exe /S" architecture="x86" />
+
+    <upgrade include="remove" />
+    <upgrade include="install" />
+    <!-- old version of package had a non-helpful revision number=920 so newer
+         wpkg versions count as downgrades -->
+    <downgrade include="remove"/>
+    <downgrade include="install" />
+
+    <!-- try to remove 9.20, but don't complain if it's not currently installed -->
+    <remove  cmd='msiexec /qn /x{23170F69-40C1-2701-0920-000001000000}'>
+      <exit code="1605" />
+    </remove>
+
+    <remove cmd='cmd.exe /c  start "" /b /wait "%programfiles%\7-zip\uninstall.exe" /S'>
+      <condition>
+        <check type="file" condition="exists" path="%programfiles%\7-zip\uninstall.exe"/>
+      </condition>
+    </remove>
+
+  </package>
+</packages>