In the user guide I read:
20.2. Accessing the web via a proxy > Configuring an HTTP proxy (for example for downloading dependencies) is done via standard JVM system properties. These properties > can be set directly in the build script; for example System.setProperty(‘http.proxyHost’, ‘www.somehost.org’) for the proxy host.
Alternatively, the properties can be specified in a gradle.properties file, either in the build’s root directory or
in the Gradle home directory.
Shouldn’t this be 'in the Gradle user home directory* ?