Add FindCrypt in the users module.

src/modules/users/CMakeModules/FindCrypt.cmake

@@ -0,0 +1,23 @@
+# - Find libcrypt
+# Find the libcrypt includes and the libcrypt libraries
+# This module defines
+# LIBCRYPT_INCLUDE_DIR, root crypt include dir. Include crypt with crypt.h
+# LIBCRYPT_LIBRARY, the path to libcrypt
+# LIBCRYPT_FOUND, whether libcrypt was found
+
+
+find_path( CRYPT_INCLUDE_DIR NAMES crypt.h
+    HINTS
+        ${CMAKE_INSTALL_INCLUDEDIR}
+)
+
+find_library( CRYPT_LIBRARIES NAMES crypt
+    HINTS
+        ${CMAKE_INSTALL_LIBDIR}
+)
+
+include( FindPackageHandleStandardArgs )
+find_package_handle_standard_args( Crypt
+                                   REQUIRED_VARS CRYPT_LIBRARIES CRYPT_INCLUDE_DIR )
+
+mark_as_advanced( CRYPT_INCLUDE_DIR CRYPT_LIBRARIES )