fix: compatible with windows path in Robolectric test.

[alps2006]

Problem

When running Robolectric in windows os, following error can occur.

java.util.regex.PatternSyntaxException: Unexpected internal error near index 1
\
	at java.base/java.util.regex.Pattern.error(Pattern.java:2027)
	at java.base/java.util.regex.Pattern.compile(Pattern.java:1788)
	at java.base/java.util.regex.Pattern.<init>(Pattern.java:1428)
	at java.base/java.util.regex.Pattern.compile(Pattern.java:1068)
	at java.base/java.lang.String.split(String.java:2317)
	at java.base/java.lang.String.split(String.java:2364)
	at ch.qos.logback.core.rolling.helper.FileFinder.regexEscapePath(Unknown Source)
	at ch.qos.logback.core.rolling.helper.FileNamePattern.toRegex(Unknown Source)
	at ch.qos.logback.core.rolling.helper.DateParser.<init>(Unknown Source)
	at ch.qos.logback.core.rolling.helper.TimeBasedArchiveRemover.<init>(Unknown Source)
	at ch.qos.logback.core.rolling.helper.SizeAndTimeBasedArchiveRemover.<init>(Unknown Source)
	at ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP.createArchiveRemover(Unknown Source)
	at ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP.start(Unknown Source)
	at ch.qos.logback.core.rolling.TimeBasedRollingPolicy.start(Unknown Source)

Because String.split() method use a regex parameter, but there may be a \ in windows OS.

Resolving

In logback, log path was slashified, so i always use a / to split pattern and path.