cmd/go: fix PGO script flag matching

build_pgo.txt hard-coded a check for / rather than using ${/}, causing a
failure on Windows

The failure in build_pgo_auto_multi.txt is more interesting. If the
first argument to stdout starts with `-` the script engine expects it to
be a flag to grep, and thus doesn't regexp-escape `\` in the expansion
of `${/}`.

The script engine doesn't _require_ that these are flags to grep, so it
is still possible to use them for matching, but this ideally will change
in the future, so change all patterns to avoid starting with `-`.

Fixes #60408.

Change-Id: Ie4041a730d22ce40a4436abae7713f211dcb42e4
Reviewed-on: https://go-review.googlesource.com/c/go/+/497881
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

0 files changed, 0 insertions, 0 deletions