[Build] Use String.strip() instead of trim()

[HannesWell]

This also reverts

• Use trim() instead of strip() because Jenkins doesn't like it now. #3007

[HannesWell]

In fact String.trim() already does trim line-breaks. Its Javadoc says:

Returns a string whose value is this string, with all leading and trailing space removed,
where space is defined as any character whose codepoint is less than or equal to 'U+0020' (the space character).

Thanks @merks for pointing this out.
So this change is not necessary in practice. Closing.