Framework build fails with permission error

[ryandesign]

Trying to compile the hexfiend framework fails on the MacPorts automated build system as follows:

CompileXIB framework/resources/HFModalProgress.xib
    cd /opt/local/var/macports/build/_opt_mports_dports_editors_hexfiend/HexFiend-framework/work/HexFiend-2.3.0
    export XCODE_DEVELOPER_USR_PATH=/Applications/Xcode.app/Contents/Developer/usr/bin/..
    /Applications/Xcode.app/Contents/Developer/usr/bin/ibtool --errors --warnings --notices --minimum-deployment-target 10.9 --output-format human-readable-text --compile /opt/local/var/macports/build/_opt_mports_dports_editors_hexfiend/HexFiend-framework/work/HexFiend-2.3.0/build/Release/HexFiend.framework/Versions/A/Resources/HFModalProgress.nib /opt/local/var/macports/build/_opt_mports_dports_editors_hexfiend/HexFiend-framework/work/HexFiend-2.3.0/framework/resources/HFModalProgress.xib
/* com.apple.ibtool.document.notices */
/opt/local/var/macports/build/_opt_mports_dports_editors_hexfiend/HexFiend-framework/work/HexFiend-2.3.0/framework/resources/HFModalProgress.xib:4: note: View is clipping its content
/* com.apple.ibtool.errors */
/opt/local/var/macports/build/_opt_mports_dports_editors_hexfiend/HexFiend-framework/work/HexFiend-2.3.0/framework/resources/HFModalProgress.xib: error: Compilation failed. Unable to write to path: /opt/local/var/macports/build/_opt_mports_dports_editors_hexfiend/HexFiend-framework/work/HexFiend-2.3.0/build/Release/HexFiend.framework/Versions/A/Resources/HFModalProgress.nib
    Underlying Errors:
        Description: You don’t have permission to save the file “HFModalProgress.nib” in the folder “Resources”.
        Failure Reason: You don’t have permission.
        Recovery Suggestion: To view or change permissions, select the item in the Finder and choose File > Get Info.
        Underlying Errors:
            Description: The operation couldn’t be completed. Operation not permitted
            Failure Reason: Operation not permitted
        Description: “HFModalProgress.nib” couldn’t be removed.
        Failure Reason: The file doesn’t exist.
        Underlying Errors:
            Description: The operation couldn’t be completed. No such file or directory
            Failure Reason: No such file or directory

Builds occur in a clean build directory, so no manual changing of permissions in the build directory are expected to be required.

[percontation]

I saw this error once for the HexFiend port (not the HexFiend-framework subport), but can no longer reproduce it. The port file I am testing with is basically the 2.1.2 one, with just the checksums changed and the patch stuff removed.