use uname(2) instead of /proc/, this allows to run nginx in chroot

src/os/unix/ngx_linux_config.h

diff --git a/src/os/unix/ngx_linux_config.h b/src/os/unix/ngx_linux_config.h
index 3e0475f..c584ff8 100644
--- a/src/os/unix/ngx_linux_config.h
+++ b/src/os/unix/ngx_linux_config.h
@@ -50,6 +50,7 @@
 #include <sys/ioctl.h>
 #include <sys/sysctl.h>
 #include <crypt.h>
+#include <sys/utsname.h>        /* uname() */
 
 
 #include <ngx_auto_config.h>