ext/pcntl: pcntl_unshare minor error message clarification (for EINVAL). (#13872)

it is not necessarily a bad flag but can just be unsupported by the
current kernel.

Author: devnexen

ext/pcntl/pcntl.c

@@ -1262,7 +1262,7 @@ PHP_FUNCTION(pcntl_unshare)
 		switch (errno) {
 #ifdef EINVAL
 			case EINVAL:
-				zend_argument_value_error(1, "must be a combination of CLONE_* flags");
+				zend_argument_value_error(1, "must be a combination of CLONE_* flags, or at least one flag is unsupported by the kernel");
 				RETURN_THROWS();
 				break;
 #endif

ext/pcntl/tests/pcntl_unshare_04.phpt

@@ -23,4 +23,4 @@ try {
 
 ?>
 --EXPECT--
-pcntl_unshare(): Argument #1 ($flags) must be a combination of CLONE_* flags
+pcntl_unshare(): Argument #1 ($flags) must be a combination of CLONE_* flags, or at least one flag is unsupported by the kernel