Add test for interaction of --gc-sections and undefined references
Add test for interaction of --gc-sections and undefined references

It is possible for a link to fail with an undefined reference, unless
--gc-sections is specified, removing the reference in the process. This
doesn't look to be tested anywhere explicitly, so I thought it useful
to add a test for it to ensure the behaviour is maintained.

Reviewers: ruiu

Differential Revision: https://reviews.llvm.org/D42299


git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@323099 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld