[roll third_party/pigweed] pw_env_setup: Only add mingw to PATH once

MinGW was getting added to the PATH once for every package. This change
ensures that MinGW only gets added to the PATH if it actually exists in
the package.

Original-Bug: b/322437881
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/190030

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 525d409ba89ae26..065ec0f8496dcaf
Roller-URL: https://ci.chromium.org/b/8757250037251469521
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie813a714f50845ecd3ef0ddf17fb3a2b1ab42c46
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/190131
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 525d409..065ec0f 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 525d409ba89ae26d7ecced84ef38143002887399
+Subproject commit 065ec0f8496dcafca5a09ecf8953bd8c4fd40329