Pip install of Basilisk directory erroneously interprets stderr content as a failure

[patkenneally]

Describe the bug
On line 310 in conanfile.py the Basilisk directory is pip installed. This line interprets any output to stderr (returned in the err variable) as an error. However, characters in stderr don't necessarily mean an error. Rather, this line should call process.returncode and check for a success 0, or error code 1 or otherwise.

To reproduce
Steps to reproduce the behavior:
NA

Expected behavior
Check process.returncode, log stderr output in any case.

Screenshots
NA

Desktop (please complete the following information):

• OS: Macos
• Version 13.6
• Python version 3.9.15

Additional context
Add any other context about the problem or potential solution paths here.