Fix WindowsBuilder executable path and enhance MSI linking error reporting

- Updated the path to the built executable to reflect changes in the output structure.
- Added calculation and display of total distribution size after build.
- Enhanced error reporting for the MSI linking process by capturing and printing stdout and stderr output.
- Updated WiX source file to include UI namespace for better compatibility.
- Removed unnecessary blank line in test_msi.py for cleaner code.

build/WebDropBridge.wxs

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
+<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi"
+     xmlns:ui="http://schemas.microsoft.com/wix/2010/ui">
     <Product Id="*" Name="WebDrop Bridge" Language="1033" Version="0.5.0"
         Manufacturer="HIM-Tools"
         UpgradeCode="12345678-1234-1234-1234-123456789012">