Make requesting SDES available only on Fuchsia builds

Bug: webrtc:11066
Change-Id: I0707cf63064830a55db31e883dc7b15aa675950b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/257900
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36438}

pc/peer_connection_integrationtest.cc

@@ -269,6 +269,7 @@ TEST_P(PeerConnectionIntegrationTest, EndToEndCallWithDtls) {
                                     webrtc::kEnumCounterKeyProtocolSdes));
 }
 
+#if defined(WEBRTC_FUCHSIA)
 // Uses SDES instead of DTLS for key agreement.
 TEST_P(PeerConnectionIntegrationTest, EndToEndCallWithSdes) {
   PeerConnectionInterface::RTCConfiguration sdes_config;
@@ -292,6 +293,7 @@ TEST_P(PeerConnectionIntegrationTest, EndToEndCallWithSdes) {
       0, webrtc::metrics::NumEvents("WebRTC.PeerConnection.KeyProtocol",
                                     webrtc::kEnumCounterKeyProtocolDtls));
 }
+#endif
 
 // Basic end-to-end test specifying the `enable_encrypted_rtp_header_extensions`
 // option to offer encrypted versions of all header extensions alongside the