[roll third_party/pigweed] Fixes for GCC 10 compatibility

- pw_kvs: Remove use of std::enable_if that wasn't working property.
- pw_result, pw_rpc: Disable spurious GCC 10 warnings.
- pw_string: Size report code that is never executed was using the same
  pointer for snprintf input and output, which is not legal. This caused
  -Wrestrict warnings. Update the size report code to avoid this.
- Add the -pthread flag in GCC host builds to support building
  pw_thread.
- pw_tokenizer: For host builds, insert the tokenizer sections after
  .debug_info instead of .strtab, since inserting after .strtab does not
  work for GCC.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/40620

third_party/pigweed Rolled-Commits: 47a4304ca6b1a38..a77e5e7a1cfca3b
Roller-URL: https://ci.chromium.org/b/8850131779790436272
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8850131779790436272
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I89615eee39560e26a44d8eb6e1d1b2f0cc7e89a8
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/40662
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 47a4304..a77e5e7 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 47a4304ca6b1a38fc2e1a6c5c5b719af2bf9a30c
+Subproject commit a77e5e7a1cfca3b109e1bcf6536444080e6bee44