[SR-724] Update build-script, etc. to support building from a source directory not called 'swift'

[rudkx]

Previous ID	SR-724
Radar	None
Original Reporter	@rudkx
Type	Task

Additional Detail from JIRA

Votes	0
Component/s
Labels	Task
Assignee	None
Priority	Medium

md5: 21d1b973029308dde4fda272bd8bca62

Issue Description:

It would be great to update our build so that the 'swift' source directory does not need to be called 'swift'.

This would be great to have so that people can use 'git worktree' easily, e.g.:
git worktree add -b bug-fix ../bug-fix
cd ../bug-fix
[edit stuff]
git commit -m 'fix the bug!'
./utils/build-script -rT --build-subdir=../build/bug-fix-build

[Dante-Broggi]

Has this been done? If so, this should be closed.

[rudkx]

I tried this again relatively recently and it was still an issue.