go/build: call ctxt.match for checking file name constraints
This makes the checking of build tags in file names consistent to that of the build tags in `// +build` line.
Fixed #25461
Change-Id: Iba14d1050f8aba44e7539ab3b8711af1980ccfe4
GitHub-Last-Rev:
11b14e239dd85e11e669919aab45494aee7c59a3
GitHub-Pull-Request: golang/go#25480
Reviewed-on: https://go-review.googlesource.com/113818
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>