Update minimum CI versions to 6.4

...and to Xcode 26.4 (Swift 6.3) on macOS. This drops support for Swift 6.2 on Apple platforms, and for 6.3 elsewhere.

Author: jakepetroules

.github/workflows/pull_request.yml

@@ -21,14 +21,14 @@ jobs:
       linux_os_versions: '["amazonlinux2", "bookworm", "noble", "jammy", "rhel-ubi9"]'
       linux_pre_build_command: ./.github/scripts/prebuild.sh
       linux_build_command: 'swift test --no-parallel'
-      linux_swift_versions: '["nightly-main", "nightly-6.3"]'
+      linux_swift_versions: '["nightly-main", "nightly-6.4.x"]'
       linux_host_archs: '["x86_64", "aarch64"]'
       freebsd_pre_build_command: ./.github/scripts/prebuild.sh
       freebsd_build_command: 'swift test --no-parallel'
       enable_freebsd_checks: true
       windows_build_timeout: 180
       windows_pre_build_command: 'Invoke-Program .\.github\scripts\prebuild.ps1'
-      windows_swift_versions: '["nightly-main", "nightly-6.3"]'
+      windows_swift_versions: '["nightly-main", "nightly-6.4.x"]'
       windows_build_command: 'Invoke-Program swift test --no-parallel'
       enable_linux_static_sdk_build: true
       enable_android_sdk_build: true
@@ -37,7 +37,7 @@ jobs:
       linux_static_sdk_build_command: SWIFTBUILD_STATIC_LINK=1 LLBUILD_STATIC_LINK=1 swift build
       enable_ios_checks: true
       enable_macos_checks: true
-      macos_exclude_xcode_versions: "[{\"xcode_version\": \"16.3\"}, {\"xcode_version\": \"16.4\"}]"
+      macos_exclude_xcode_versions: "[{\"xcode_version\": \"16.4\"}, {\"xcode_version\": \"26.3\"}]"
       macos_pre_build_command: ./.github/scripts/prebuild.sh
       macos_build_command:
         swift test &&
@@ -51,7 +51,7 @@ jobs:
       enable_windows_docker: false
       windows_build_timeout: 180
       windows_pre_build_command: 'Invoke-Program .\.github\scripts\prebuild.ps1'
-      windows_swift_versions: '["nightly-main", "nightly-6.3"]'
+      windows_swift_versions: '["nightly-main", "nightly-6.4.x"]'
       windows_build_command: 'Invoke-Program swift test --no-parallel'
       windows_os_versions: '["windows-2022", "windows-11-arm"]'
   cmake-smoke-test:

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:6.0
+// swift-tools-version:6.2
 
 //===----------------------------------------------------------------------===//
 //