multicast_iperf: Check if iperf is installed

To avoid doing an unnecessary download and build of iperf, check if the
application is present before building.

Killing the netserver with -9 is unneccessary and will lead to a non-0
exit status. Change to -2, and move to use the more widely available
pkill command.

Tested by running: multicast_iperf

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
time drift test: Avoid build if available

Tested by running: check_clock_offset.with_syscall

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
pipetest application: Avoid building if available

Tested by running: ipi_x2apic

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
nx exploit application: Avoid building if available

Tested by running: nx

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
clock_getres application: Avoid building if available

Tested by running: clock_getres

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
stress: Avoid building if available

Tested by running: softlockup

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
virtual_nic_send_buffer: Fix building of udt

- Only try to install libraries to /usr/lib64 if the guest is x86_64:
  Some (usually 64-bit only) installations only have /usr/lib.

- Use && instead of ; to check for any errors in compilation, instead of
  discovering them when trying to run sendfile/recvfile

- Improve error output when building failed by saving and including the
  error message when raising an exception

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
udt/sendfile/recvfile: Avoid building if available

Tested by running: virtual_nic_send_buffer

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>