cmd/go: fix formatting of file paths under cwd
The output of go with -x flag is formatted in a manner that file paths
under current directory are modified to start with a dot (.), but when
the directory path ends with a slash (/), the formatting goes wrong.
Fixes #23982
Change-Id: I8f8d15dd52bee882a9c6357eb9eabdc3eaa887c3
GitHub-Last-Rev:
1493f38bafdf2c40f16392b794fd1a12eb12a151
GitHub-Pull-Request: golang/go#23985
Reviewed-on: https://go-review.googlesource.com/95755
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>