scripts: add build tests

scripts: add build tests

This script helps to build a list of target with some custom options.
It tries to enable most of the options.
The examples and documentation are also built.

It uses some configuration from exported variables.
This config works on my machine:
export DPDK_DEP_PCAP=y
export DPDK_DEP_MOFED=y
       mlxdep=/opt/mofed-3.0
export DPDK_DEP_CFLAGS=-I$mlxdep/include
export DPDK_DEP_LDFLAGS=-L$mlxdep/lib
export DPDK_BUILD_TEST_CONFIGS='x86_64-native-linuxapp-gcc+shared+next
       x86_64-native-linuxapp-clang+shared+combined
       i686-native-linuxapp-gcc+combined'
export DPDK_MAKE_JOBS=8
export DPDK_NOTIFY=notify-send

Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>
v2:
- conditionally enable szedata2
- add quotes for CFLAGS and LDFLAGS