[Boost-build] Remove <flavor>mingw from gcc

Subject: [Boost-build] Remove <flavor>mingw from gcc
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2014-04-07 13:27:44

AMDG

The fact the the gcc toolset automatically sets
the flavor to mingw has several unfortunate
consequences:
- MinGW does not interact well with non-mingw (such
  as cygwin or when running mingw as a cross compiler.),
  without extra work, because <toolset-gcc:flavor>mingw
  becomes the default.
- The Boost.Build tests are failing because of the
  failure to parse gcc-mingw-4.5.4 when the toolsets
  are not declared in user-config.jam.

I propose simply removing this behavior.

I searched the Boost tree and the only place I
could find that refers to <toolset-gcc:flavor>mingw
is common.format-name which uses mgw instead of gcc
as the toolset name.  This check can be changed to
use <target-os>windows instead.

Any objections?

In Christ,
Steven Watanabe