Compile external dependencies with /O1 in Windows Bazel builds.

Pass /O1 via --per_file_copt=external/.* on Windows so external test dependencies such as GoogleTest and RE2 are compiled with size optimization instead of full /O2 in opt builds or unoptimized /Od in dbg builds, reducing both compile time and debug test execution overhead without affecting Abseil's own optimization flags.

PiperOrigin-RevId: 1005099651

.bazelrc

diff --git a/.bazelrc b/.bazelrc
index 3427eb2..af3db69 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -41,14 +41,16 @@
 common:windows-msvc --enable_runfiles
 build:windows-msvc --cxxopt=/std:c++17 --host_cxxopt=/std:c++17
 build:windows-msvc --copt=/WX
-build:windows-msvc --per_file_copt=external/.*@/w
-build:windows-msvc --host_per_file_copt=external/.*@/w
+build:windows-msvc --per_file_copt=external/.*@/w,/O1
+build:windows-msvc --host_per_file_copt=external/.*@/w,/O1
+test:windows-msvc --build_tests_only
 
 build:windows-clangcl --config=windows-msvc
 build:windows-clangcl --compiler=clang-cl
 build:windows-clangcl --copt=-Wno-microsoft-cast
 build:windows-clangcl --extra_execution_platforms=//:x64_windows-clang-cl
 build:windows-clangcl --extra_toolchains=@local_config_cc//:cc-toolchain-x64_windows-clang-cl
+test:windows-clangcl --nobuild_tests_only
 
 # Configure our macOS Xcode setup.
 build:macos --cxxopt=-std=c++17 --host_cxxopt=-std=c++17
@@ -92,6 +94,8 @@
 build:remote-cache --remote_download_regex=.*symbolize_test\.pdb$
 # Retry up for up to 15 minutes under heavy load (exponential backoff).
 build:remote-cache --remote_retries=20 --remote_retry_max_delay=60s
+# Use more parallel jobs for remote cache lookups and tests.
+build:remote-cache --jobs=HOST_CPUS*4
 
 build:remote-base --define=EXECUTOR=remote
 build:remote-base --remote_timeout=1200 --bes_timeout=600s