Get net_unittests working on Windows BoringSSL port.

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index 3dcfa6b588a220f41413faafc6da64d5600f521b..2101250b6d44ddca1bdce99fd49c5f09b18d2f29 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -249,6 +249,11 @@ component("net") {
         "cert/cert_verify_proc_nss.h",
       ]
     }
+    if (is_win) {
+      sources -= [
+        "cert/cert/sha256_legacy_support_nss_win.cc',
+      ]
+    }
   } else {
     sources -= [
       "base/crypto_module_openssl.cc",
@@ -284,6 +289,7 @@ component("net") {
     }
     if (is_win) {
       sources -= [
+        "cert/cert/sha256_legacy_support_openssl_win.cc',
         "ssl/openssl_platform_key_win.cc",
       ]
     }