qt6_tool.py: Fix expanding multiple config keys per line

re.match() matches the complete line, so it works only
at the beginning. Use re.search() instead.
Rename the "match" variable to avoid clashes with the keyword.

Change-Id: I11ec7b5aed9eee4cf8feca63964381d038b079d8
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>