fixing subprocess build on linux

Author: ktoso

Package.swift

@@ -83,6 +83,14 @@ let javaIncludePath = "\(javaHome)/include"
   let javaPlatformIncludePath = "\(javaIncludePath)/win32"
 #endif
 
+let subprocessSwiftSettings: [SwiftSetting] = [
+  .define(
+    "SYSTEM_PACKAGE_DARWIN",
+    .when(platforms: [.macOS, .macCatalyst, .iOS, .watchOS, .tvOS, .visionOS])),
+  .define("SYSTEM_PACKAGE"),
+  .define("ENABLE_MOCKING", .when(configuration: .debug)),
+]
+
 let package = Package(
   name: "SwiftJava",
   platforms: [
@@ -369,9 +377,9 @@ let package = Package(
         "JavaKitShared",
         "JavaKitConfigurationShared",
         // .product(name: "Subprocess", package: "swift-subprocess")
-        "_Subprocess", // using process spawning
+        "_Subprocess",
       ],
-      swiftSettings: [
+      swiftSettings: subprocessSwiftSettings + [
         .swiftLanguageMode(.v5),
         .enableUpcomingFeature("BareSlashRegexLiterals"),
         .unsafeFlags(["-I\(javaIncludePath)", "-I\(javaPlatformIncludePath)"]),
@@ -394,8 +402,7 @@ let package = Package(
         "JavaKitShared",
         "JavaKitConfigurationShared",
       ],
-
-      swiftSettings: [
+      swiftSettings: subprocessSwiftSettings + [
         .swiftLanguageMode(.v5),
         .unsafeFlags(["-I\(javaIncludePath)", "-I\(javaPlatformIncludePath)"]),
         .enableUpcomingFeature("BareSlashRegexLiterals"),
@@ -497,13 +504,13 @@ let package = Package(
     // Experimental Foundation Subprocess Copy
     .target(
       name: "_SubprocessCShims",
-      swiftSettings: [
+      swiftSettings: subprocessSwiftSettings + [
         .swiftLanguageMode(.v5)
       ]
     ),
     .target(
       name: "_Subprocess",
-      dependencies: [
+      dependencies: subprocessSwiftSettings + [
         "_SubprocessCShims",
         .product(name: "SystemPackage", package: "swift-system"),
       ],