Fixes warnings when building python3.dll due to the .def file accumulating multiple copies of each line.

Adds shebang line to prepare_ssl so it will run with py.exe.

PCbuild/prepare_ssl.py

@@ -1,3 +1,4 @@
+#! /usr/bin/env python3
 # Script for preparing OpenSSL for building on Windows.
 # Uses Perl to create nmake makefiles and otherwise prepare the way
 # for building on 32 or 64 bit platforms.

PCbuild/python3dll.vcxproj

@@ -109,7 +109,7 @@
       </_Lines>
     </ItemGroup>
     <MakeDir Directories="$(IntDir)" />
-    <WriteLinesToFile File="$(IntDir)python3_d.def" Lines="@(_Lines->'%(New)')" />
+    <WriteLinesToFile File="$(IntDir)python3_d.def" Lines="@(_Lines->'%(New)')" Overwrite="true" />
   </Target>
   
   <Target Name="BuildStubDef" BeforeTargets="PreLinkEvent" Inputs="..\PC\python3.def" Outputs="$(IntDir)python3stub.def">
@@ -132,7 +132,7 @@
       <_Lines Include="@(_Symbols->'%(Symbol)')" />
     </ItemGroup>
     <MakeDir Directories="$(IntDir)" />
-    <WriteLinesToFile File="$(IntDir)python3stub.def" Lines="@(_Lines)" />
+    <WriteLinesToFile File="$(IntDir)python3stub.def" Lines="@(_Lines)" Overwrite="true" />
   </Target>
   <Target Name="_CleanStubDef" BeforeTargets="CoreClean">
     <ItemGroup>