LLDB/GDB plugin: add support for coredumpctl in unittests, and fix LldbTest::testCoreFile
Summary:
In case a coredump file wasn't generated directly, try to invoke coredumpctl to get it.
Also, this patch fixes debug session hanging on starting state when use LLDB as backend.
Test Plan: GdbTest::testCoreFile and LldbTest::testCoreFile
Reviewers: kfunk, KDevelop, mwolff
Reviewed By: KDevelop, mwolff
Subscribers: mwolff, kdevelop-devel
Differential Revision: https://phabricator.kde.org/D2604