[MacPorts] #53791: llvm-4.0: update to release tarball, remove subversion dependency

[MacPorts]

#53791: llvm-4.0: update to release tarball, remove subversion dependency
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 Reporter:  sierkb  |      Owner:
     Type:  update  |     Status:  new
 Priority:  Normal  |  Milestone:
Component:  ports   |    Version:
 Keywords:          |       Port:  llvm-4.0
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 LLVM 4.0.0 release has been officially announced on Mar 13 2017:
 ​http://lists.llvm.org/pipermail/llvm-dev/2017-March/111025.html.
 Download sources and several prebuild binaries ​for this version are
 available on http://www.llvm.org/releases/download.html#4.0.0.

 Since official stable source tarballs are now available from the project's
 website, there seems to be no further need to use the svn checkout.
 Therefore, please change the svn checkout in favor to the official
 provided tarballs and so remove the subversion dependency which should
 remain for the ''llvm-devel'' port, where it makes more sense. As done on
 all other previous stable llvm ports before.

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Ticket URL: <https://trac.macports.org/ticket/53791>
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