Added --use-system-layout option to boost formula

[nkakuev]

I've added the '--use-system-layout' option to boost formula. It passes the '--layout=system' option instead of regular '--layout=tagged' to bjam and thus removes the '-mt' suffix from resulting binaries.

The case is, the default value of this option on unix-like systems (including os x) is 'system' as it is stated in bjam man page:

The default value is 'versioned' on Windows, and
'system' on Unix.
It produces binaries without any suffixes (i. e. 'libboost_chrono.a' instead of 'libboost_chrono-mt.a') which I find very handy, because a lot of software that links with boost searches for libraries without any suffixes in their names.

The 'tagged' layout (which boost formula is using at the moment) is dedicated to be used in case of several variants of Boost mostly:

tagged -- Names of boost binaries include the
encoded build properties such as variant and
threading, but do not including compiler name
and version, or Boost version. This option is
useful if you build several variants of Boost,
using the same compiler.

I see no reason in limiting the layout to 'tagged' only.

[adamv]

What does MacPorts do?

[nkakuev]

It uses '--layout=tagged'.

[manphiz]

IMHO tagged layout is reasonable because package may break if linked to the wrong type of libraries. It might also be beneficial to use versioned as now there are 2 to 3 compilers in Mac OS X, and they are somewhat not fully compatible. The problem here may be how to get the correct ${LDFLAGS} for software using boost. Currently there's no built-in tools in boost to do this.

Autotools user can take advantage of autoconf-archive which contains several m4 files for boost which handles all flavor of library names (they actually try to find all 'libboost-.*.{so,dylib.a}'). Not sure about other tools though.

[adamv]

Other maintainers: help me out here when you get a chance.

[MikeMcQuaid]

This pull seems reasonable. Rebase and I'll merge.