\c senfutil automatically parses SCons command line arguments into the SCons build
environment. This allows specifying any parameter on the command line:
<pre>
- $ scons CXXCOM=mygcc CXXFLAGS+=-mtune=geode
+ $ scons CXX=myg++ CXXFLAGS+=-mtune=geode
</pre>
You may either set variables unconditionally using '=' or append values to the end of a list
using '+='.