Fix gdbserver build failure on targets without fork

This commit fixes nat/linux-namespaces.c to build correctly on
targets without fork.

gdb/ChangeLog:

	* nat/linux-namespaces.c (do_fork): New function.
	(linux_mntns_get_helper): Use the above.

gdb/gdbserver/ChangeLog:

	* configure.ac (AC_FUNC_FORK): New check.
	* config.in: Regenerate.
	* configure: Likewise.

1 files changed, 14 insertions, 1 deletions

diff --git a/gdb/nat/linux-namespaces.c b/gdb/nat/linux-namespaces.c
index fb1467ca09..e9626ab913 100644
--- a/gdb/nat/linux-namespaces.c
+++ b/gdb/nat/linux-namespaces.c
@@ -32,6 +32,19 @@
 /* See nat/linux-namespaces.h.  */
 int debug_linux_namespaces;
 
+/* Handle systems without fork.  */
+
+static inline pid_t
+do_fork (void)
+{
+#ifdef HAVE_FORK
+  return fork ();
+#else
+  errno = ENOSYS;
+  return -1;
+#endif
+}
+
 /* Handle systems without setns.  */
 
 static inline int
@@ -644,7 +657,7 @@ linux_mntns_get_helper (void)
       if (gdb_socketpair_cloexec (AF_UNIX, SOCK_STREAM, 0, sv) < 0)
 	return NULL;
 
-      h.pid = fork ();
+      h.pid = do_fork ();
       if (h.pid < 0)
 	{
 	  int saved_errno = errno;