[MacPorts] #71253: gegl-devel @0.4.50: builds fail on 10.13/10.14: dispatch.h: error: expected value in expression (HAVE_UNISTD_H)

[MacPorts]

#71253: gegl-devel @0.4.50: builds fail on 10.13/10.14: dispatch.h: error: expected
value in expression (HAVE_UNISTD_H)
-------------------------+----------------------
  Reporter:  mascguy     |      Owner:  mascguy
      Type:  defect      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.10.4
Resolution:              |   Keywords:
      Port:  gegl-devel  |
-------------------------+----------------------

Comment (by mascguy):

 Replying to [comment:1 mascguy]:
 > Based on some quick googling, cmake-based projects fix this by using
 `#cmakedefine01 HAVE_UNISTD_H` for macOS builds:
 >
 > {{{
 > #if defined(__APPLE__) && !defined(__IOS__)
 > #cmakedefine01 HAVE_UNISTD_H
 > #else
 > #cmakedefine HAVE_UNISTD_H
 > #endif
 > }}}
 >
 > This ensures that the definition is always one or zero, rather than
 nothing.

 For gegl, perhaps we can add a fix in the Meson build, to mimic this for
 macOS builds.

-- 
Ticket URL: <https://trac.macports.org/ticket/71253#comment:2>
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