fix race condition with TSCUtility.Platform::darwinCacheDirectories (#3151)

motivation: TSCUtility.Platform::darwinCacheDirectories is not thread-safe, can cause race condition when accessing concurrently

changes: wrap TSCUtility.Platform::darwinCacheDirectories with ThreadSafeArrayStore

Author: tomerd

Sources/PackageLoading/ManifestLoader.swift

@@ -1051,7 +1051,7 @@ private func sandboxProfile(toolsVersion: ToolsVersion, cacheDirectories: [Absol
         stream <<< "(allow sysctl*)" <<< "\n"
         // Allow writing in temporary locations.
         stream <<< "(allow file-write*" <<< "\n"
-        for directory in Platform.darwinCacheDirectories() {
+        for directory in Platform.threadSafeDarwinCacheDirectories.get() {
             stream <<< ##"    (regex #"^\##(directory.pathString)/org\.llvm\.clang.*")"## <<< "\n"
         }
         for directory in cacheDirectories {
@@ -1063,6 +1063,10 @@ private func sandboxProfile(toolsVersion: ToolsVersion, cacheDirectories: [Absol
     return stream.bytes.description
 }
 
+extension TSCUtility.Platform {
+    internal static let threadSafeDarwinCacheDirectories = ThreadSafeArrayStore<AbsolutePath>(Self.darwinCacheDirectories())
+}
+
 extension TSCBasic.Diagnostic.Message {
     static func duplicateTargetName(targetName: String) -> Self {
         .error("duplicate target named '\(targetName)'")