Add missing glibc import

Author: Lukasa

Sources/Foundation/Process.swift

@@ -20,6 +20,10 @@ import Darwin
 import WinSDK
 #endif
 
+#if canImport(Glibc)
+@_implementationOnly import Glibc
+#endif
+
 extension Process {
     public enum TerminationReason : Int {
         case exit