Adds -Wsign-conversion to LLVM warnings for non-test code since

Chromium builds Abseil with this warning.

Tests are still built with -Wno-sign-conversion due to many pre-existing
warnings.

PiperOrigin-RevId: 496438882
Change-Id: Ic47c893e5289d3d45cd5717ba02d5499a3b346fa

absl/copts/GENERATED_AbseilCopts.cmake

@@ -97,6 +97,7 @@ list(APPEND ABSL_LLVM_FLAGS
     "-Wself-assign"
     "-Wshadow-all"
     "-Wshorten-64-to-32"
+    "-Wsign-conversion"
     "-Wstring-conversion"
     "-Wtautological-overlap-compare"
     "-Wtautological-unsigned-zero-compare"

absl/copts/GENERATED_copts.bzl

@@ -98,6 +98,7 @@ ABSL_LLVM_FLAGS = [
     "-Wself-assign",
     "-Wshadow-all",
     "-Wshorten-64-to-32",
+    "-Wsign-conversion",
     "-Wstring-conversion",
     "-Wtautological-overlap-compare",
     "-Wtautological-unsigned-zero-compare",

absl/copts/copts.py

@@ -58,6 +58,7 @@ ABSL_LLVM_FLAGS = [
     "-Wself-assign",
     "-Wshadow-all",
     "-Wshorten-64-to-32",
+    "-Wsign-conversion",
     "-Wstring-conversion",
     "-Wtautological-overlap-compare",
     "-Wtautological-unsigned-zero-compare",