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I am currently trying to build a version of opencv, featuring cuda, on my arch linux computer. For that, I use opencv-cuda-git as base version. Additionally, I modified the PKGBUILD and added additional flags to further adapt opencv to my system.

However, everytime I run the buildprocess (makepkg csri), it fails with following error message:

[ 16%] Building CXX object modules/hdf/CMakeFiles/example_hdf_create_groups.dir/samples/create_groups.cpp.o
cd /home/tobias/builds/opencv-cuda-git/src/opencv/build/modules/hdf && /usr/bin/cmake -E cmake_link_script CMakeFiles/example_hdf_create_groups.dir/link.txt --verbose=1
/bin/g++-6 -std=c++11 -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winit-self -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-comment -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffast-math -ffunction-sections -fdata-sections -msse -msse2 -fvisibility=hidden -fvisibility-inlines-hidden -Wno-invalid-offsetof -O3 -DNDEBUG -DNDEBUG -Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now -Wl,--gc-sections -rdynamic CMakeFiles/example_hdf_create_groups.dir/samples/create_groups.cpp.o -o ../../bin/example_hdf_create_groups -L/opt/cuda/lib64 ../../lib/libopencv_hdf.so.3.4.0 ../../lib/libopencv_highgui.so.3.4.0 ../../lib/libopencv_videoio.so.3.4.0 ../../lib/libopencv_imgcodecs.so.3.4.0 ../../lib/libopencv_imgproc.so.3.4.0 ../../lib/libopencv_core.so.3.4.0 ../../lib/libopencv_cudev.so.3.4.0 
../../lib/libopencv_core.so.3.4.0: undefined reference to `cblas_zgemm'
../../lib/libopencv_core.so.3.4.0: undefined reference to `cblas_sgemm'
../../lib/libopencv_core.so.3.4.0: undefined reference to `cblas_dgemm'
../../lib/libopencv_core.so.3.4.0: undefined reference to `cblas_cgemm'
make[2]: *** [modules/hdf/CMakeFiles/example_hdf_create_groups.dir/build.make:102: bin/example_hdf_create_groups] Error 1
make[2]: Leaving directory '/home/tobias/builds/opencv-cuda-git/src/opencv/build'
make[1]: *** [CMakeFiles/Makefile2:2523: modules/hdf/CMakeFiles/example_hdf_create_groups.dir/all] Error 2
make[1]: Leaving directory '/home/tobias/builds/opencv-cuda-git/src/opencv/build'
make: *** [Makefile:163: all] Error 2

My previous search suggested that this error might occur due to a linking error with cublas. Therefore I tried to add -L/opt/cuda/lib64 and -lcublas to CMAKE_CXX_FLAGS. That made no difference at all.

Suggestions by another blog contained using gcc-6 instead of g++-6. That however yields another error:

[ 16%] Linking CXX executable ../../bin/example_hdf_create_groups
cd /home/tobias/builds/opencv-cuda-git/src/opencv/build/modules/hdf && /usr/bin/cmake -E cmake_link_script CMakeFiles/example_hdf_create_groups.dir/link.txt --verbose=1
/bin/gcc-6 -std=c++11 -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winit-self -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-comment -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffast-math -ffunction-sections -fdata-sections -msse -msse2 -fvisibility=hidden -fvisibility-inlines-hidden -Wno-invalid-offsetof -O3 -DNDEBUG -DNDEBUG -Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now -Wl,--gc-sections -rdynamic CMakeFiles/example_hdf_create_groups.dir/samples/create_groups.cpp.o -o ../../bin/example_hdf_create_groups -L/opt/cuda/lib64 ../../lib/libopencv_hdf.so.3.4.0 ../../lib/libopencv_highgui.so.3.4.0 ../../lib/libopencv_videoio.so.3.4.0 ../../lib/libopencv_imgcodecs.so.3.4.0 ../../lib/libopencv_imgproc.so.3.4.0 ../../lib/libopencv_core.so.3.4.0 ../../lib/libopencv_cudev.so.3.4.0 
ld: CMakeFiles/example_hdf_create_groups.dir/samples/create_groups.cpp.o: undefined reference to symbol '_ZNSt8ios_base4InitD1Ev@@GLIBCXX_3.4'
/usr/lib/libstdc++.so.6: error adding symbols: DSO missing from command line
make[2]: *** [modules/hdf/CMakeFiles/example_hdf_create_groups.dir/build.make:102: bin/example_hdf_create_groups] Error 1
make[2]: Leaving directory '/home/tobias/builds/opencv-cuda-git/src/opencv/build'
make[1]: *** [CMakeFiles/Makefile2:2523: modules/hdf/CMakeFiles/example_hdf_create_groups.dir/all] Error 2
make[1]: Leaving directory '/home/tobias/builds/opencv-cuda-git/src/opencv/build'
make: *** [Makefile:163: all] Error 2

The whole output of the build process and the customized PKGBUILD file can be found here

Cuda version 9, output of nvidia-smi:

Sun Jan 14 14:44:13 2018 
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 387.34 Driver Version: 387.34 | |-------------------------------+----------------------+----------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
|===============================+======================+======================|
| 0 GeForce GTX 780 Ti Off | 00000000:01:00.0 N/A | N/A |
| 32% 27C P8 N/A / N/A | 624MiB / 3017MiB | N/A Default |
+-------------------------------+----------------------+----------------------+

+-----------------------------------------------------------------------------+
| Processes: GPU Memory |
| GPU PID Type Process name Usage |
|=============================================================================|
| 0 Not Supported |
+-----------------------------------------------------------------------------+

Okay so to close the question:

The Problem was that opencv needs both Lapack with the normal blas and cblas if you are using the ceres-solver. However, the opencv build only links cublas, which apparently lacks support for some needed functions of cblas.

One solution to this Problem was to manually link cblas by adding
CMAKE_EXE_LINKER_FLAGS=-lcblas to the cmake call in the PKGBUILD file.

It is probably possible to circumvent this problem altogether by building all dependencies manually with forced cublas support. However, that is tedious and not always possible since cublas is only a partial port.

Thanks again to Philippos, who helped me narrrow the problem down.