[MacPorts] #74402: port diagnose reports Xcode "none" as unsupported on a valid CLT-only installation

[MacPorts]

#74402: port diagnose reports Xcode "none" as unsupported on a valid CLT-only
installation
------------------------+--------------------
 Reporter:  ragtimelab  |      Owner:  (none)
     Type:  defect      |     Status:  new
 Priority:  Normal      |  Milestone:
Component:  base        |    Version:
 Keywords:  diagnose    |       Port:
------------------------+--------------------
 On macOS 15.8 with MacPorts 2.12.6, `port diagnose --quiet` reports:

 {{{
 Error: The installed version of Xcode, none, is not supported by MacPorts.
 For your currently installed system, the following versions of Xcode are
 supported:
 26.3 26.2 26.1.1 26.1 26.0.1 26.0 16.4 16.3 16.2 16.1 16.0
 }}}

 This system intentionally has no full `/Applications/Xcode.app`
 installation, but it has a valid, selected Xcode Command Line Tools
 installation:

 {{{
 $ xcode-select -p
 /Library/Developer/CommandLineTools

 $ pkgutil --pkg-info=com.apple.pkg.CLTools_Executables
 package-id: com.apple.pkg.CLTools_Executables
 version: 26.3.0.0.1.1769666919

 $ /usr/bin/xcodebuild -version
 xcode-select: error: tool 'xcodebuild' requires Xcode, but active
 developer directory '/Library/Developer/CommandLineTools' is a command
 line tools instance
 }}}

 Therefore, `xcodeversion = none` is expected here: it means that full
 Xcode is absent, not that no usable developer tools are installed.

 The diagnosis appears to compare only `xcodeversion` with the full-Xcode
 compatibility list. This produces an error even though `xcodecltversion`
 is present and usable. The normal port execution logic already
 distinguishes these cases: a port that sets `use_xcode yes` needs full
 Xcode, while ordinary ports can use valid Command Line Tools.

 Expected behavior:
 When full Xcode is absent but valid Command Line Tools are installed,
 `port diagnose` should not report that Xcode `none` is unsupported. It
 could pass this check or emit a distinct informational message that only
 `use_xcode=yes` ports require full Xcode.

 This is distinct from #73438 (a newer installed full-Xcode version not yet
 listed), #63130 (missing CLT receipts or broken SDKs), #59691
 (intermittent inability to detect an installed full Xcode on Snow
 Leopard), and #63377 (wording for newer full-Xcode versions).

-- 
Ticket URL: <https://trac.macports.org/ticket/74402>
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