Revert "scons: Enable building through Clang Static Analyzer."

Revert "scons: Enable building through Clang Static Analyzer."

This reverts commit a45a50a4828e1357e9555474bc127c5585b3a420.

Unfortunately gcc dumps argv[0] as the first word of --version, so it is
unreliable for detecting gcc.

In particular `cc --version` and `i686-w64-mingw32-gcc --version` give
wrong results.

A better solution needs to be found -- most likely using C-preprocessing
like autotools does.  Revert for now.