chore: Update build to be out of source

[ciband]

Updated build to be out of source to clean up the workspace
and added build scripts to enforce this.

Re-enabled cmake_example builds in CI.

Removed cmake_example .gitmodules file. This historically caused
git to do funny things having a nested .gitmodules in the source
tree. Commented out the submodule clone in the CMakeList.txt and
setup the build script to mimic the submodule clone by copying the
cpp-crypto source into the correct directory.

What kind of change does this PR introduce?

• Bugfix
• Feature
• Refactor
• Performance
• Tests
• Build
• Documentation
• Code style update
• Continuous Integration
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

Does this PR release a new version?

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the develop branch, not the master branch
• All tests are passing
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

[ghost]

Thanks for submitting this pull request! A maintainer will review this in the next few days and explicitly select labels so you know what's going on.

If no reviewer appears after a week, a reminder will be sent out.

[ciband]

Clang tidy is failing and I'm not sure why. There is a lot of noise in the output from curl and what not.

I think a future PR to limit clang tidy file processing to not process submodules is needed.

We can either merge this PR as is or we can hold until we can reduce the clang tidy output such that the error is easier to spot.

[ciband]

Update: It appears that clang tidy is failing on a curl source file:

Line 63249:
error: error reading '/home/circleci/project/src/lib/curl/src/tool_hugehelp.c' [clang-diagnostic-error]

Line 177893:
error: error reading '/home/circleci/project/src/lib/curl/tests/libtest/lib1521.c' [clang-diagnostic-error]

I do not know why.

[faustbrian]

@ciband conflicts

[ciband]

@sleepdefic1t , @faustbrian Clang build failure looks like a circle ci issue. I am unable to re-trigger, if desired.

[ghost]

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Thank you for your contribution!

[ghost]

A contributor has approved this PR. A maintainer will merge this PR shortly. If it shouldn't be merged yet, please leave a comment saying so and we'll wait.

Thank you for your contribution!

[ghost]

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