Summary
There are some places in the WT build process that reference /opt/mongodbtoolchain/gdb. All references to /opt/mongodbtoolchain/gdb should look for the gdb binary in /opt/mongodbtoolchain/v3/bin instead.

Motivation

• Does this affect any team outside of WT?
  We are doing the same thing for SERVER builds.

• How likely is it that this use case or problem will occur?
  This affects all builds.

• If the problem does occur, what are the consequences and how severe are they?
  The /opt/mongodbtoolchain/gdb path is very old and blocks our ability to deprecate the location in the v4 toolchain.

• Is this issue urgent?
  No, but it should be done before WT moves off the v3 toolchain.

Acceptance Criteria (Definition of Done)
The /opt/mongodbtoolchain/gdb path is no longer referenced in the codebase.

• Testing
  A debug build of WT should still succeed.

• Documentation update
  No.

[Optional] Suggested Solution
All references to /opt/mongodbtoolchain/gdb should look for the gdb binary in /opt/mongodbtoolchain/v3/bin instead.