Library can't find libgomp.1.dylib despite it's being present - gcc

Question

I'm trying to build OpenSfM on my M1 MacBook. I installed GCC11, Ceres and OpenCV via MacPorts. I needed to add /opt/local/lib manually to OpenSfM's CMakeLists.txt as setuptools somehow didn't find ceres.h, but afterwards compiling OpenSfM worked fine.
When I later on run a program that uses OpenSfM, it fails with:
Traceback (most recent call last):
File "/Users/pvitt/projects/odm/./run.py", line 19, in <module>
from stages.odm_app import ODMApp
File "/Users/pvitt/projects/odm/stages/odm_app.py", line 10, in <module>
from stages.run_opensfm import ODMOpenSfMStage
File "/Users/pvitt/projects/odm/stages/run_opensfm.py", line 14, in <module>
from opendm.osfm import OSFMContext
File "/Users/pvitt/projects/odm/opendm/osfm.py", line 14, in <module>
from opensfm.large import metadataset
File "/opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/opensfm-0.5.2-py3.9.egg/opensfm/large/metadataset.py", line 7, in <module>
from opensfm import io
File "/opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/opensfm-0.5.2-py3.9.egg/opensfm/io.py", line 11, in <module>
from opensfm import context, features, geo, pygeometry, pymap, types
File "/opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/opensfm-0.5.2-py3.9.egg/opensfm/features.py", line 9, in <module>
from opensfm import context, pyfeatures
ImportError: dlopen(/opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/opensfm-0.5.2-py3.9.egg/opensfm/pyfeatures.cpython-39-darwin.so, 2): Library not loaded: #rpath/libgomp.1.dylib
Referenced from: /opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/opensfm-0.5.2-py3.9.egg/opensfm/pyfeatures.cpython-39-darwin.so
Reason: image not found
Having a look into /opt/local/lib/ shows me that there is a libgomp.1.dylib:
% ls -al /opt/local/lib/gcc11/libgomp.1.dylib
lrwxr-xr-x 1 root admin 37 May 16 00:57 /opt/local/lib/gcc11/libgomp.1.dylib -> /opt/local/lib/libgcc/libgomp.1.dylib
% ls -al /opt/local/lib/libgcc/libgomp.1.dylib
-rwxr-xr-x 1 root admin 245120 May 16 00:24 /opt/local/lib/libgcc/libgomp.1.dylib
[EDIT]
As my CPU architecture is ARM, I need to have the tools and libs also build for this architecture, what they are:
% file `which gcc`
/opt/local/bin/gcc: Mach-O 64-bit executable arm64
% file /opt/local/lib/opencv4/libopencv_core.4.5.2.dylib
/opt/local/lib/opencv4/libopencv_core.4.5.2.dylib: Mach-O 64-bit dynamically linked shared library arm64
% file /opt/local/lib/gcc11/libgomp.1.dylib
/opt/local/lib/gcc11/libgomp.1.dylib: Mach-O 64-bit dynamically linked shared library arm64
[/EDIT]
So I'm wondering where the error is coming from. Did I do a mistake during compilation? How can I find the reason for this error? As I also had to add /opt/local/lib manually to the CMakeLists.txt file, I suspect that this path is somehow not published properly. But how comes that a folder where MacPorts puts all it's stuff is not used by cmake? Do I have to publish it manually? Via CPATH/LIBRARY_PATH? And why can I just use OpenMP:
% cat test_omp.c
#include <stdio.h>
#include <omp.h>
void main() {
#pragma omp parallel
{
printf("Hello World... from thread = %d\n", omp_get_thread_num());
}
}
% gcc -fopenmp test_omp.c
% ./a.out
Hello World... from thread = 1
Hello World... from thread = 3
Hello World... from thread = 2
Hello World... from thread = 5
Hello World... from thread = 4
Hello World... from thread = 6
Hello World... from thread = 0
Hello World... from thread = 7
I fear it is something really silly, but I just don't see it.