[roll third_party/pigweed] pw_toolchain: Remove "dummy" toolchain

Original-Bug: 386
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/46924

third_party/pigweed Rolled-Commits: bcaf883773fc10a..e8aa18975353659
Roller-URL: https://ci.chromium.org/b/8846143667671799200
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8846143667671799200
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Iee62cadc89c68305ba4119634627badb219efba8
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/47101
Reviewed-by: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index bcaf883..e8aa189 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit bcaf883773fc10ac614b60593ab565b1a721e7fb
+Subproject commit e8aa18975353659695810443a12e14b27b7a69c0