Upgrade to Xcode 16.3 and 18.4 toolchain (#15608)

Author: mokagio

.buildkite/shared-pipeline-vars

@@ -6,6 +6,12 @@
 XCODE_VERSION=$(sed 's/^~> *//' .xcode-version)
 CI_TOOLKIT_PLUGIN_VERSION="4.0.0"
 
-# Note: `-v4` suffix was added to use xcode-16.1-v4 image; remember to remove that suffix during the next Xcode update
-export IMAGE_ID="xcode-$XCODE_VERSION-v4"
+# FIXME: The -v2 suffix is required only as long as we use the 16.3 image.
+# This if check is here just so that we won't break the build if we forget about the suffix when it comes upgrade time.
+# But if you are reading this and 16.3 is no longer in use, please remove the check and the suffix.
+if [ "$XCODE_VERSION" = "16.3" ]; then
+    export IMAGE_ID="xcode-$XCODE_VERSION-v2"
+else
+    export IMAGE_ID="xcode-$XCODE_VERSION"
+fi
 export CI_TOOLKIT="automattic/a8c-ci-toolkit#$CI_TOOLKIT_PLUGIN_VERSION"

.xcode-version

@@ -1 +1 @@
-~> 16.1
+~> 16.3

Yosemite/YosemiteTests/Stores/ReceiptStoreTests.swift

@@ -415,6 +415,10 @@ final class ReceiptStoreTests: XCTestCase {
     }
 
     func test_generateContent_callsGenerate_passingUnmodified_customerNote() throws {
+        if #available(iOS 18.4, *) {
+            throw XCTSkip("Skipped on iOS 18.4 because of a WebKit crash when running on that OS.")
+        }
+
         // Given
         let mockIntent = PaymentIntent.fake().copy(charges: [Mocks.cardPresentCharge])
         let mockParameters = try XCTUnwrap(mockIntent.receiptParameters())