[MacPorts] #56294: boost: update to 1.70.0

[MacPorts]

#56294: boost: update to 1.70.0
------------------------+---------------------------------
  Reporter:  michaelld  |      Owner:  ryandesign
      Type:  update     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:
Resolution:             |   Keywords:  haspatch maintainer
      Port:  boost      |
------------------------+---------------------------------

Comment (by michaelld):

 The Portfile section to get the CMake scripts installed where at least
 some ports do so (`share/cmake`), is:
 {{{
 pre-destroot {
     destroot.args {*}${build.args} --prefix=${destroot}${prefix} \
         --cmakedir=${destroot}${prefix}/share/cmake
     system "find ${worksrcpath} -type f -name '*.gch' -exec rm {} \\;"
 }
 }}}
 note to `--cmakedir` addition. Without this tweak they are installed into
 `lib/cmake`.

 Not sure which is the better location, but after a quick review of the
 ports I have that install into both of these, I'm actually inclines to
 leave the install in `lib/cmake`. Anyone have an opinion about this?

-- 
Ticket URL: <https://trac.macports.org/ticket/56294#comment:23>
MacPorts <https://www.macports.org/>
Ports system for macOS