libomp installs files outside normal destroot folders

[neverpanic (Clemens Lang)]

--->  Computing dependencies for libomp
--->  Fetching archive for libomp
--->  Attempting to fetch libomp-18.1.2_0.darwin_22.x86_64.tbz2 from https://fra.de.packages.macports.org/libomp
--->  Attempting to fetch libomp-18.1.2_0.darwin_22.x86_64.tbz2 from https://packages.macports.org/libomp
--->  Attempting to fetch libomp-18.1.2_0.darwin_22.x86_64.tbz2 from https://nue.de.packages.macports.org/libomp
--->  Fetching distfiles for libomp
--->  Attempting to fetch openmp-18.1.2.src.tar.xz from https://releases.llvm.org/18.1.2
--->  Attempting to fetch openmp-18.1.2.src.tar.xz from https://distfiles.macports.org/openmp-release
--->  Attempting to fetch cmake-18.1.2.src.tar.xz from https://releases.llvm.org/18.1.2
--->  Attempting to fetch cmake-18.1.2.src.tar.xz from https://distfiles.macports.org/openmp-release
--->  Verifying checksums for libomp
--->  Extracting libomp
Warning: The following existing file was hidden from the build system by trace mode:
  /private/var/select/sh
--->  Applying patches to libomp
Warning: The following existing file was hidden from the build system by trace mode:
  /private/var/select/sh
--->  Configuring libomp
Warning: The following existing files were hidden from the build system by trace mode:
  /System/Cryptexes/OS/System/Library/CoreServices/SystemVersion.plist
  /opt
  /private/var/select/sh
  /usr/X11R6
--->  Building libomp
Warning: The following existing files were hidden from the build system by trace mode:
  /opt
  /opt/local/lib/perl5/vendor_perl/5.34/Getopt/Long.pm
  /opt/local/lib/perl5/vendor_perl/5.34/darwin-thread-multi-2level/Data/Dumper.pm
  /opt/local/lib/perl5/vendor_perl/5.34/darwin-thread-multi-2level/Encode.pm
  /opt/local/lib/perl5/vendor_perl/5.34/darwin-thread-multi-2level/Encode/Alias.pm
  /opt/local/lib/perl5/vendor_perl/5.34/darwin-thread-multi-2level/Encode/Config.pm
  /opt/local/lib/perl5/vendor_perl/5.34/darwin-thread-multi-2level/Encode/Encoding.pm
  /opt/local/lib/perl5/vendor_perl/5.34/darwin-thread-multi-2level/Encode/MIME/Name.pm
  /opt/local/lib/perl5/vendor_perl/5.34/darwin-thread-multi-2level/XSLoader.pm
  /private/var/select/sh
--->  Staging libomp into destroot
Warning: The following existing files were hidden from the build system by trace mode:
  /opt
  /private/var/select/sh
  /var/root/.CFUserTextEncoding
Warning: violation by /opt/local/tmp
Warning: libomp violates the layout of the ports-filesystems!
Warning: Please fix or indicate this misbehavior (if it is intended), it will be an error in future releases!
--->  Installing libomp @18.1.2_0

Does libomp have a good reason for installing files in /opt/local/tmp? Could it use $TMPDIR instead, or at least /opt/local/var/tmp?

The installed file is /include/opmx.h, which sounds like it should be in /opt/local/include instead:

:) cllang@cllang-mac:~$ port contents libomp | grep '/opt/local/tmp'
  /opt/local/tmp/include/ompx.h

[neverpanic (Clemens Lang)]

main.log of an affected run, run with sudo port -vt destroot.

[ryandesign (Ryan Carsten Schmidt)]

Duplicate of #69557.