Improved the capabilities feature detection. Previously included file sys/capability.h mentioned in capset(2) man page, belongs to the libcap-dev package, which may not be installed on some Linux systems when compiling nginx. This prevented the capabilities feature from being detected and compiled on that systems. Now linux/capability.h system header is included instead. Since capset() declaration is located in sys/capability.h, now capset() syscall is defined explicitly in code using the SYS_capset constant, similarly to other Linux-specific features in nginx.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


cat << END >> $NGX_AUTO_CONFIG_H

#ifndef $have
#define $have  $value
#endif

END