[m-rev.] diff: replace use of the Java security manager

[Julien Fischer]

Replace use of the Java security manager.

The security manager was deprecated in Java 17 and recent versions of Java now
emit warnings about its use; replace its use.

library/io.call_system.m:
     Instead of using the security manager methods to check whether
     "/bin/sh" is executable, use the methods provided by the java.nio
     package.

Julien.

diff --git a/library/io.call_system.m b/library/io.call_system.m
index 161e100..c9d0d45 100644
--- a/library/io.call_system.m
+++ b/library/io.call_system.m
@@ -207,15 +207,8 @@ call_system_return_signal(Command, Result, !IO) :-
  "
      boolean has_sh;
      try {
-        SecurityManager sm = System.getSecurityManager();
-        if (sm != null) {
-            sm.checkExec(""/bin/sh"");
-            has_sh = true;
-        } else {
-            // If there is no security manager installed, we just check
-            // if the file exists.
-            has_sh = new java.io.File(""/bin/sh"").exists();
-        }
+        has_sh = java.nio.file.Files.isExecutable(
+            java.nio.file.Paths.get(""/bin/sh""));
      } catch (java.lang.Exception e) {
          has_sh = false;
      }
@@ -262,7 +255,7 @@ call_system_return_signal(Command, Result, !IO) :-
              throw stderr.exception;
          }
      } catch (java.lang.Exception e) {
-        Status  = 1;
+        Status = 1;
          Error = e;
      }
  ").