Add support for new Android overlay, swiftlang/swift#74758 (#286)

Author: finagolfin

Sources/Crypto/Key Derivation/HKDF.swift

@@ -15,6 +15,9 @@
 @_exported import CryptoKit
 #else
 import Foundation
+#if canImport(Android)
+import Android
+#endif
 
 /// A standards-based implementation of an HMAC-based Key Derivation Function
 /// (HKDF).

Sources/_CryptoExtras/Key Derivation/Scrypt/BoringSSL/Scrypt_boring.swift

@@ -21,6 +21,10 @@ import Foundation
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
 
+#if canImport(Android)
+import Android
+#endif
+
 internal struct BoringSSLScrypt {
     /// Derives a secure key using the provided passphrase and salt.
     ///