[MacPorts] #65839: xar: Remove icu dependency and avoid overlinking to libxml2's dependencies

[MacPorts]

#65839: xar: Remove icu dependency and avoid overlinking to libxml2's dependencies
------------------------+-------------------------
 Reporter:  ryandesign  |      Owner:  Schamschula
     Type:  defect      |     Status:  assigned
 Priority:  Normal      |  Milestone:
Component:  ports       |    Version:  2.7.2
 Keywords:              |       Port:  xar
------------------------+-------------------------
 In [8f9c15ffae374e6da5d4e5697e3697644275c6ef/macports-ports] a dependency
 on icu was added to the xar port. It should be removed because xar does
 not use icu. It only uses libxml2, and libxml2 happens to use icu.

 The reason why xar ends up linked with icu and libxml2's other internal
 dependencies (libiconv, liblzma) is that it uses `xml2-config` to find
 libxml2, and `xml2-config` by default assumes you will be making static
 libraries. It's the same problem reported against old versions of php in
 #59439.

 The solution is to add the `--dynamic` flag when invoking `xml2-config
 --libs`. (The `--dynamic` flag is a fairly recent addition to
 `xml2-config` and probably didn't exist when xar was being developed.)
 I'll send a PR.

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Ticket URL: <https://trac.macports.org/ticket/65839>
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