Building IGV fails with the following error message:

---
src/utils/IdealGraphVisualizer$ ant build

Buildfile: src/utils/IdealGraphVisualizer/build.xml

download:
     [echo] Downloading clusters ide|platform
      [get] Getting: http://bits.netbeans.org/dev/nbms-and-javadoc/lastSuccessfulBuild/artifact/nbbuild/netbeans/harness/tasks.jar
      [get] To: /tmp/tasks.jar
      [get] http://bits.netbeans.org/dev/nbms-and-javadoc/lastSuccessfulBuild/artifact/nbbuild/netbeans/harness/tasks.jar moved to https://netbeans.apache.org/about/oracle-transition.html
      [get] .
      [get] last modified = Fri Mar 05 06:41:47 CET 2021

BUILD FAILED
src/utils/IdealGraphVisualizer/build.xml:7: The following error occurred while executing this line:
src/utils/IdealGraphVisualizer/nbproject/build-impl.xml:41: The following error occurred while executing this line:
src/utils/IdealGraphVisualizer/nbproject/platform.xml:28: taskdef class org.netbeans.nbbuild.AutoUpdate cannot be found
 using the classloader AntClassLoader[/tmp/tasks.jar]
---

The failure is due to the recent transition of the NetBeans project to the Apache fundation.

WORKAROUND
Remove the temporary file that has been downloaded (e.g. /tmp/tasks.jar in the above message) and run:

src/utils/IdealGraphVisualizer$ ant -Dbootstrap.url=https://repo1.maven.org/maven2/org/codehaus/mojo/nbm-maven-harness/7.4/nbm-maven-harness-7.4.jar build