Swift: Fix Windows build

Adds some flags for Swift's LLVM compiler to succeed on Windows.

Related: https://github.com/llvm/llvm-project/issues/40056

Signed-off-by: kingbri <bdashore3@proton.me>

Package.swift

@@ -18,7 +18,7 @@ var sources = [
 
 var resources: [Resource] = []
 var linkerSettings: [LinkerSetting] = []
-var cSettings: [CSetting] =  [
+var cSettings: [CSetting] = [
     .unsafeFlags(["-Wno-shorten-64-to-32", "-O3", "-DNDEBUG"]),
     .unsafeFlags(["-fno-objc-arc"]),
     // NOTE: NEW_LAPACK will required iOS version 16.4+
@@ -27,6 +27,8 @@ var cSettings: [CSetting] =  [
     // .define("ACCELERATE_NEW_LAPACK"),
     // .define("ACCELERATE_LAPACK_ILP64")
 ]
+var cxxSettings: [CXXSetting] = []
+var cxxStandard: CXXLanguageStandard = .cxx11
 
 #if canImport(Darwin)
 sources.append("ggml/src/ggml-metal.m")
@@ -44,6 +46,14 @@ cSettings.append(
     cSettings.append(.define("_GNU_SOURCE"))
 #endif
 
+#if canImport(WinSDK)
+    // See https://github.com/llvm/llvm-project/issues/40056
+    cxxSettings.append(.unsafeFlags(["-Xclang", "-fno-split-cold-code"]))
+
+    // MSVC errors below C++ 14
+    cxxStandard = .cxx14
+#endif
+
 let package = Package(
     name: "llama",
     platforms: [
@@ -75,5 +85,5 @@ let package = Package(
             linkerSettings: linkerSettings
         )
     ],
-    cxxLanguageStandard: .cxx11
+    cxxLanguageStandard: cxxStandard
 )