[Boost-build] Help request from a newbie: unable to build 64 target with Visual 2010

Subject: [Boost-build] Help request from a newbie: unable to build 64 target with Visual 2010
From: Michel Lerenard (michelisotropix_at_[hidden])
Date: 2012-04-19 11:55:24

Hi everyone,

I've been pulling my hair all day because I cannot build the 64 bits 
libraries with visual. ( I have no issue building the 32bits targets) I 
have the 1.49 package.
I keep getting the following message every time the linker tries to 
create a lib.

bin.v2\libs\system\build\msvc-10.0\release\threading-multi\error_code.obj : 
fatal error LNK1112: module machine type 'X86' conflicts with target 
machine type 'x64'

Naively i thought i forgot to set the flag for the x64 target, as the 
link command looked like:
link /NOLOGO /INCREMENTAL:NO /DLL /MACHINE:X86 /subsystem:console /
out:"bin.v2\libs\system\build\msvc-10.0\release\threading-multi\boost_system-vc1
00-mt-1_49.dll" 
/IMPLIB:"bin.v2\libs\system\build\msvc-10.0\release\threading-mu
lti\boost_system-vc100-mt-1_49.lib"   /MACHINE:x64 
@"bin.v2\libs\system\build\ms
vc-10.0\release\threading-multi\boost_system-vc100-mt-1_49.dll.rsp"

Sadly that not enough; running the command

b2 --address-model=64 -j2 link=shared threading=multi variant=release 
linkflags="/MACHINE:x64"

i get the error:
link /NOLOGO /INCREMENTAL:NO /DLL /MACHINE:X64 /MACHINE:X86 
/subsystem:console /
out:"bin.v2\libs\system\build\msvc-10.0\release\threading-multi\boost_system-vc1
00-mt-1_49.dll" 
/IMPLIB:"bin.v2\libs\system\build\msvc-10.0\release\threading-mu
lti\boost_system-vc100-mt-1_49.lib"   /MACHINE:x64 
@"bin.v2\libs\system\build\ms
vc-10.0\release\threading-multi\boost_system-vc100-mt-1_49.dll.rsp"

As you can see, the fun begins when the linker uses TWO targets flags in 
its command. I'm quite lost here, i've tried almost everything: editing 
the jam configuration file to take the platform x64 into account (next 
to amd64), switching to visual 2008, changing the Visual command line 
shortcut to use the "x64" parameter.

Still in the log, i see the line :
call "C:\Program Files (x86)\Microsoft Visual Studio 
10.0\VC\vcvarsall.bat" x86 >nul.

I guess that one reason why the compiler gets the wrong flag, but how 
can i modify this one ?

I'll appreciate every bit of help i can get...