[MacPorts] #69789: nettle 3.9.1_0: won't build on macOS 14 / XCode 15.3

[MacPorts]

#69789: nettle 3.9.1_0: won't build on macOS 14 / XCode 15.3
--------------------+--------------------
 Reporter:  rbeyer  |      Owner:  (none)
     Type:  defect  |     Status:  new
 Priority:  Normal  |  Milestone:
Component:  ports   |    Version:  2.9.3
 Keywords:          |       Port:  nettle
--------------------+--------------------
 When I try and build nettle on my M3 macOS 15 system under XCode 15.3, it
 yields this error:

 ```:info:build xcode-select: Failed to locate 'm4', requesting
 installation of command line developer tools.```

 A dialog is opened asking if I want to install.  However, after doing
 that, and then attempting to rebuild the port, the same exact error
 happens.  So I'm not entirely sure what's wrong.  Earlier in the build log
 (attached), there are messages saying that m4 is in the build tree and is
 found, but then later when clang runs, I guess it is trying to look for it
 in the command line developer tools, and I'm not sure why it can't be
 found?

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Ticket URL: <https://trac.macports.org/ticket/69789>
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