[MacPorts] #68488: mlton on 10.6 x86_64 tries to build for 32 bit (and fails on linking)

[MacPorts]

#68488: mlton on 10.6 x86_64 tries to build for 32 bit (and fails on linking)
---------------------------+---------------------------------
  Reporter:  barracuda156  |      Owner:  barracuda156
      Type:  defect        |     Status:  assigned
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:  2.8.1
Resolution:                |   Keywords:  snowleopard, x86_64
      Port:  mlton         |
---------------------------+---------------------------------

Comment (by ryandesign):

 Indeed, it is using the `-m32` flag, which is probably a result of the
 erroneous assumption that the output of `uname -m` is the desired userland
 architecture. On macOS, it's the kernel architecture, and on some x86_64
 machines running Mac OS X 10.6 the kernel is 32-bit, which is of course
 not a problem at all for running 64-bit userland programs.

 https://github.com/MLton/mlton/blob/92137753df8c003e0628bf10a676eef492fe47b3/bin/platform#L73-L75
 \\
 https://github.com/MLton/mlton/blob/92137753df8c003e0628bf10a676eef492fe47b3/bin/platform#L146-L148
 \\
 https://github.com/MLton/mlton/blob/92137753df8c003e0628bf10a676eef492fe47b3/runtime/Makefile#L105-L107

 While that's a bug that could be reported upstream if they care to fix
 their assumptions about ancient versions of macOS, for MacPorts we should
 fix the Portfile so that it does not allow the build system to make
 assumptions; MacPorts should dictate to the build system what architecture
 to build for, since the user may wish to override it by setting
 `build_arch` in macports.conf.

-- 
Ticket URL: <https://trac.macports.org/ticket/68488#comment:1>
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