lldb: don't issue command when there's no env variables to set, fix Bug 391897
Summary:
LLDB becomes stricter about the settings set target.env-vars
command. Now it doens't allow empty arguments. This causes a warning
when start debugging session in KDevelop.
https://bugs.kde.org/show_bug.cgi?id=391897
Test Plan:
- Created a new project with an empty environment variable profile
- Start debugging with lldb
- No warnings
Reviewers: apol, KDevelop
Reviewed By: apol, KDevelop
Subscribers: kdevelop-devel
Differential Revision: https://phabricator.kde.org/D11524
(cherry picked from commit 3fd20921df6a9d69c54bfc1add86f42185652148)