Use SecKeychainCopyDomainSearchList to find system keychain

[mlink]

It's been mentioned on the forums that hardcoding a path to the system keychain may not be ideal. This PR addresses that by using the Security frameworks methods to locate the system keychain. To retain compatibility any errors from attempting to locate the system keychain will default to previous behavior and return a reference to KeychainFile that will attempt to find the system keychain at /Library/Keychains/System.keychain.

[JacobHearst]

LGTM, just some linting errors to clean up

[mlink]

LGTM, just some linting errors to clean up

If I could push…

remote: Resolving deltas: 100% (4/4), completed with 4 local objects.
remote: error: GH006: Protected branch update failed for refs/heads/ml_use_keychain_search_list_to_find_system_keychain.
remote: error: Cannot change this locked branch

Do I need to submit another PR to merge into this one?

[JacobHearst]

LGTM, just some linting errors to clean up

If I could push…

remote: Resolving deltas: 100% (4/4), completed with 4 local objects.
remote: error: GH006: Protected branch update failed for refs/heads/ml_use_keychain_search_list_to_find_system_keychain.
remote: error: Cannot change this locked branch

Do I need to submit another PR to merge into this one?

Uhhhh not sure why this branch is locked... let me take a look through the repo settings

EDIT: Found the rule, not 100% sure why it's there so checking with @macblazer

[JacobHearst]

@mlink The reason branches are locked is that the preferred workflow for internal and external contributors is to fork this repo and make a PR that way. Please close this PR, fork Haversack, and make your changes that way.

[macblazer]

The Contributing section of the README does say to fork this repo and make your changes in the fork.