[build] Bump mac_sdk_min to 14.0.

TEST=ci
Change-Id: I92eb459a037ce8e4d1f98d1e28d7fd483f08f242
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/468883
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Brian Quinlan <bquinlan@google.com>

build/config/mac/mac_sdk.gni

@@ -6,11 +6,7 @@ import("//build/toolchain/rbe.gni")
 
 declare_args() {
   # Minimum supported version of the Mac SDK.
-  #
-  # TODO: When the minimum supported SDK version is incremented to "10.15",
-  # remove the usage of `SecTrustEvaluate` from
-  # runtime/bin/security_context_macos.cc
-  mac_sdk_min = "10.14"
+  mac_sdk_min = "14.0"
 
   # Path to a specific version of the Mac SDK, not including a backslash at
   # the end. If empty, the path to the lowest version greater than or equal to

runtime/bin/security_context_macos.cc

@@ -9,7 +9,6 @@
 
 #include "bin/security_context.h"
 
-#include <Availability.h>
 #include <CoreFoundation/CoreFoundation.h>
 #include <Security/SecureTransport.h>
 #include <Security/Security.h>
@@ -289,11 +288,6 @@ static void TrustEvaluateHandler(Dart_Port dest_port_id,
   }
 
   // Perform the certificate verification.
-  // The result is ignored as we get more information from the following call
-  // to SecTrustGetTrustResult which also happens to match the information we
-  // got from calling SecTrustEvaluate before macOS 10.14.
-  bool res = SecTrustEvaluateWithError(trust.get(), nullptr);
-  USE(res);
   OSStatus status = SecTrustGetTrustResult(trust.get(), &trust_result);
 
   postReply(reply_port_id,