Fix failures when the build directory name contains +

[nobu]

What was the end-user or developer problem that led to this PR?

Fixes #6749.

What is your fix for the problem, implemented in this PR?

1. Use assert_include instead of assert_match if the expected string doesn't contain regexp metacharacters,
   Or escape the expected string with Regexp.quote.
2. Skip @tempdir contains +.

Make sure the following tasks are checked

• Describe the problem / feature
• Write tests for features and bug fixes
• Write code to solve the problem
• Make sure you follow the current code style and write meaningful commit messages without tags

[deivid-rodriguez]

Thanks!