allow true dynamic linking for Linux build
allow true dynamic linking for Linux build

Currently the binary generated from a Linux build is dynamically linked
but we force the static version for libstdc++ and libgcc.

Let's use the standard dynamic libraries for Linux to ease the tool
integration into Buildroot build system [1].

But also keep the option to build with the static stdc++ libraries as
some people apparently need it:
 # cmake -D'STATIC=1' .
 # make

[1] http://lists.busybox.net/pipermail/buildroot/2019-May/250858.html

Signed-off-by: Gary Bisson <3f1373862f751ff51c2c66833a4a3e1fe750826c@gmail.com>

NXPmicro/mfgtools,NXPmicro/mfgtools,NXPmicro/mfgtools