Check the newly introduced 'ECLIPSE_I_BUILD_TEST' environment variable
to disable the 'InjectionOSGiTest.ensureJavaxIsNotAvailable()' test case
in I-build tests.
The previous attempt to disable it failed.

Fixes https://github.com/eclipse-platform/eclipse.platform/issues/1098
Requires
https://github.com/eclipse-platform/eclipse.platform.releng.aggregator/pull/2031