nacltest.bash: remove syscall/fstest_nacl.go after test

Fixes #9232.

Change-Id: I11a7fb7691d9e7473620db1b7fa29fec359c73d3
Reviewed-on: https://go-review.googlesource.com/9642Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>

src/nacltest.bash

@@ -78,3 +78,5 @@ GOROOT=$GOROOT_BOOTSTRAP $gobin/go run ../misc/nacl/mkzip.go -p syscall -r .. ..
 # Run standard build and tests.
 export PATH=$(pwd)/../misc/nacl:$PATH
 GOOS=nacl GOARCH=$naclGOARCH ./all.bash
+
+rm -f syscall/fstest_nacl.go