Tests: adjust PackageModelTests for Windows

Adjust the path spelling for the native path arc separator and escaping
for the encoding in the JSON.

Author: compnerd

Tests/PackageModelTests/DestinationTests.swift

@@ -35,8 +35,8 @@ private let destinationV1 = (
     json: #"""
     {
         "version": 1,
-        "sdk": "\#(bundleRootPath.appending(sdkRootDir))",
-        "toolchain-bin-dir": "\#(bundleRootPath.appending(toolchainBinDir))",
+        "sdk": "\#(bundleRootPath.appending(sdkRootDir)._nativePathString(escaped: true))",
+        "toolchain-bin-dir": "\#(bundleRootPath.appending(toolchainBinDir)._nativePathString(escaped: true))",
         "target": "\#(linuxGNUTargetTriple.tripleString)",
         "extra-cc-flags": \#(extraFlags.cCompilerFlags),
         "extra-swiftc-flags": \#(extraFlags.swiftCompilerFlags),
@@ -51,7 +51,7 @@ private let destinationV2 = (
     {
         "version": 2,
         "sdkRootDir": "\#(sdkRootDir)",
-        "toolchainBinDir": "\#(toolchainBinDir)",
+        "toolchainBinDir": "\#(toolchainBinDir.pathString.replacingOccurrences(of: "\\", with: "\\\\"))",
         "hostTriples": ["\#(hostTriple.tripleString)"],
         "targetTriples": ["\#(linuxGNUTargetTriple.tripleString)"],
         "extraCCFlags": \#(extraFlags.cCompilerFlags),
@@ -330,7 +330,7 @@ final class DestinationTests: XCTestCase {
                 $0 as? StringError,
                 StringError(
                     """
-                    Couldn't parse toolset configuration at `/tools/asdf.json`: /tools/asdf.json doesn't exist in file \
+                    Couldn't parse toolset configuration at `\(AbsolutePath("/tools/asdf.json")._nativePathString(escaped: false))`: \(AbsolutePath("/tools/asdf.json")._nativePathString(escaped: false)) doesn't exist in file \
                     system
                     """
                 )
@@ -349,7 +349,7 @@ final class DestinationTests: XCTestCase {
         )) {
             XCTAssertTrue(
                 ($0 as? StringError)?.description
-                    .hasPrefix("Couldn't parse toolset configuration at `/tools/invalidToolset.json`: ") ?? false
+                    .hasPrefix("Couldn't parse toolset configuration at `\(AbsolutePath("/tools/invalidToolset.json")._nativePathString(escaped: false))`: ") ?? false
             )
         }
     }