clock_getres application: Fix build on newer gcc

Source file statements (.c, .o) needs to be before the -l calls that
include dependencies used in those source files.

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
cpu_flags: Amend to CFLAGS rather than set

Do an unconditional amend to make sure that additional CFLAGS can be
added via the make command line, while retaining the CFLAGS needed for
the build.

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
netperf_udp test: Use utils_netperf downloading

utils_netperf has code for downloading the netperf source, should the
input path be an URL. Remove the local function for doing this, and let
utils_netperf handle it instead.

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
Remove CC= from Makefiles

CC= assignments makes it impossible to supply alternate CC:s from the
command line. Additionally, CC?= does not work, as CC is set to 'cc' by
default. A possible solution might be:

ifeq ($(origin CC), default)
  CC=gcc
endif

, but seeing as cc is the preferred compiler on the target, the CC
assignment seemed unneccessary in either case.

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