Seccomp check does not detect seccomp.h if it is in different directory

It fails to detect the includedir informations from the .pc file.

['/var/lib/build/ccache/bin/gcc', '-fstack-protector-all', '-Wshadow', '-Wpacked', '-Wcast-qual', '-Wmissing-declarations', '-Wdisabled-optimization', '-Wimplicit-function-declaration', '-Winvalid-pch', '-Wpointer-arith', '-Wwrite-strings', '-Winit-self', '-Wfloat-equal', '-Wformat', '-Wformat-signedness', '-Wformat-security', '-Wsuggest-attribute=noreturn', '-fPIC', '-std=gnu99', '-O1', '-Wall', '-Wextra', '-Wmissing-prototypes', '-Wstrict-prototypes', '-Wundef', '-Wunused', '-g', '-fmessage-length=0', '-grecord-gcc-switches', '-O2', '-Wall', '-D_FORTIFY_SOURCE=2', '-fstack-protector-strong', '-funwind-tables', '-fasynchronous-unwind-tables', '-g', '-DNTPSEC_VERSION_STRING="0.9.7-9b296f5"', '-DDEBUG=1', '-DHAS_f_stack_protector_all=1', '-DHAS_PIC=1', '-DHAS_PIE=1', '-DHAS_gnu99=1', '-DHAS_w_cast_qual=1', '-DHAS_w_disabled_optimization=1', '-DHAS_w_float_equal=1', '-DHAS_w_format=1', '-DHAS_w_format_security=1', '-DHAS_w_format_signedness=1', '-DHAS_w_implicit_function_declaration=1', '-DHAS_w_init_self=1', '-DHAS_w_invalid_pch=1', '-DHAS_w_missing_declarations=1', '-DHAS_w_multichar=1', '-DHAS_w_packed=1', '-DHAS_w_pointer_arith=1', '-DHAS_w_shadow=1', '-DHAS_w_suggest_attribute_noreturn=1', '-DHAS_w_write_strings=1', '-DHAS_z_now=1', '-DHAS_relro=1', '-DHAVE_STRUCT_TIMEX=1', '-DHAVE_STRUCT_NTPTIMEVAL=1', '-DHAVE_STRUCT_TIMEX_MODES=1', '-DHAVE_STRUCT_NTPTIMEVAL_TAI=1', '-DNTP_SIZEOF_LONG=8', '-DNTP_SIZEOF_TIME_T=8', '-DOPEN_BCAST_SOCKET=1', '-DHAVE_OPENSSL_EVP_H=1', '-DHAVE_OPENSSL_RAND_H=1', '-DHAVE_OPENSSL_OBJECTS_H=1', '-DHAVE_ADJTIMEX=1', '-DHAVE_CLOCK_GETTIME=1', '-DHAVE_CLOCK_SETTIME=1', '-DHAVE_GETRUSAGE=1', '-DHAVE_NTP_ADJTIME=1', '-DHAVE_NTP_GETTIME=1', '-DHAVE_RES_INIT=1', '-DHAVE_SCHED_SETSCHEDULER=1', '-DHAVE_STRLCAT=1', '-DHAVE_STRLCPY=1', '-DHAVE_STDBOOL_H=1', '-DHAVE_ALLOCA_H=1', '-DHAVE_ARPA_NAMESER_H=1', '-DHAVE_DNS_SD_H=1', '-DHAVE_BSD_STRING_H=1', '-DHAVE_IFADDRS_H=1', '-DHAVE_LINUX_IF_ADDR_H=1', '-DHAVE_LINUX_RTNETLINK_H=1', '-DHAVE_LINUX_SERIAL_H=1', '-DHAVE_NET_ROUTE_H=1', '-DHAVE_RESOLV_H=1', '-DHAVE_SEMAPHORE_H=1', '-DHAVE_STDATOMIC_H=1', '-DHAVE_SYS_IOCTL_H=1', '-DHAVE_SYS_SYSCTL_H=1', '-DHAVE_SYS_TIMEPPS_H=1', '-DHAVE_UTMPX_H=1', '-DHAVE_SYS_TIMEX_H=1', '-DHAVE_PPSAPI=1', '-DENABLE_DROPROOT=1', '-DENABLE_DNS_LOOKUP=1', '-DHAVE_WORKING_FORK=1', '-DHAVE_KERNEL_PLL=1', '-DNEED_REUSEADDR_FOR_IFADDRBIND=1', '-DVSNPRINTF_PERCENT_M=1', "-DDIR_SEP='/'", '-DISC_PLATFORM_NORETURN_PRE=', '-DISC_PLATFORM_NORETURN_POST=__attribute__((__noreturn__))', '-DHAVE_IFLIST_SYSCTL=1', '-DHAVE_SYS_PRCTL_H=1', '-DHAVE_SYS_CAPABILITY_H=1', '-DHAVE_LINUX_CAPABILITY=1', '../../test.c', '-c', '-o/home/abuild/rpmbuild/BUILD/ntpsec-0.9.7+git20170519.9b296f50d/build/.conf_check_b2abe7ab17c3eb777f073fc8c93902f4/testbuild/main/test.c.1.o'] err: ../../test.c:2:21: fatal error: seccomp.h: No such file or directory #include <seccomp.h>

The .pc file actualy specify:

includedir=/usr/include/libseccomp Cflags: -I${includedir}

As it is obvious from the above line it is not actually respected.