Add some RTC_EXPORT needed by Chromium.

These are needed by crrev.com/c/4165083.

Bug: chromium:1369096, webrtc:14131
Change-Id: Id0a46254b46cf866f2f3b7b07b97dc55066c047f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/291117
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39165}
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index 4a9a546..7d236bc 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -839,7 +839,7 @@
     "net_helpers.cc",
     "net_helpers.h",
   ]
-  deps = []
+  deps = [ "system:rtc_export" ]
   if (is_android) {
     deps += [ ":ifaddrs_android" ]
   }
@@ -1389,6 +1389,7 @@
     "net_helper.h",
   ]
   absl_deps = [ "//third_party/abseil-cpp/absl/strings" ]
+  deps = [ "system:rtc_export" ]
 }
 
 rtc_library("socket_adapters") {