[roll third_party/pigweed] pw_toolchain: Fix divergent configuration in arm_clang M0+ toolchain

Somewhere along the way, the Cortex-M0+ lost sync with related
toolchains and introduced some configs that weren't introduced on other
toolchains. This change puts that toolchain configuration in line with
the others for consistency.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/190196

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: b415803c442d9eb..c5018fb03faf024
Roller-URL: https://ci.chromium.org/b/8757162329043210305
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I2871b46932fe8e7daf2361814973f8a30313ec78
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/190273
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 b415803..c5018fb 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b415803c442d9eb9ee2b3211489e940f8b594a20
+Subproject commit c5018fb03faf024e7570ac8d5a7cf2e790645531