Build can't resolve www.w3.org (NXDOMAIN)

The build of the new Apache NetBeans 16 release candidate fails when it tries to resolve the host 'www.w3.org'. For details, see the latest failed build on the page below:

https://launchpad.net/~jgneff/+snap/strictly-netbeans

The actual error in the build log is:

java.net.UnknownHostException: www.w3.org

Yet I can recreate the error with a build script that runs only the 'curl' and 'host' commands. The 'curl' command works, making its connection through the proxy server:

+ curl -s http://www.w3.org/2001/xml.xsd
[19/Oct/2022:20:48:19 +0000] "GET http://www.w3.org/2001/xml.xsd HTTP/1.1" 200 8836 "-" "curl/7.58.0"
<?xml version='1.0'?>
<?xml-stylesheet href="../2008/09/xsd.xsl" type="text/xsl"?>
<xs:schema targetNamespace="http://www.w3.org/XML/1998/namespace"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns ="http://www.w3.org/1999/xhtml"
  xml:lang="en">
  ...
</xs:schema>

But the 'host' command fails to resolve the host name directly:

+ host www.w3.org
Host www.w3.org not found: 3(NXDOMAIN)

Unfortunately, this direct name resolution is occurring deep within the 'javax.xml.parsers.DocumentBuilder' and 'java.net.Socket' classes of OpenJDK when trying to load an XML schema, so it's not easily bypassed in the application's build file.

Is there any way to resolve a host name behind the firewall on a Launchpad build machine?