[Boost.Build] Escape command line properly when calling assembler on MSVC

[Pekka Seppänen <pekka.seppanen@…>]

Hi.

As of Boost.Context release (since Boost 1.51.0) assembler related build rules are actually used. However, currently these make no attempt whatsoever to properly escape the command line arguments (mostly global defines, that may have characters such as "<" and ">" that are interpreted by command prompt, not good).

The following patch proxies command line arguments thru a RSP file, as done with C/C++ compiling/build rules.

The patch does

a) Add an ASM_RSPLINE under rule get-rspline,

b) Add a rule compile.asm that calls get-rspline and compile-asm,

c) Move the actual assembler call under actions compile-asm, that uses the generated ASM_RSPLINE,

d) Remove toolset.flags msvc.compile.asm DEFINES as these are now inherited from toolset.flags msvc.compile DEFINES.

That should fix it once and for all.

[Pekka Seppänen <pekka.seppanen@…>]

Add a proper command line escaping to assembler build rules.

[Pekka Seppänen <pekka.seppanen@…>]

Still broken..