Build using Visual Studio 14 project files fails to build tests

[OliverSchmitz]

cmake -G"Visual Studio 14 2015 Win64" -Dpeacock_prefix=C:\pcrteam_extern\build -Dbuild_fern=true -Dfern_git_repository=https://github.com/geoneric/fern.git -Dfern_git_tag=f67bdc78b21932025dd85b085c9bcf3464979de9 -Dfern_build_fern_algorithm=true -Dfern_build_fern_documentation=false -Dfern_build_fern_test=true C:\development\projects\peacock

fails with
C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\v140\Microsoft.CppBuild.targets(312,5): error MSB3491: Could not write lines to file "algorithm_convolution_neighborhood_square_test.dir\Release\algorith.D8FFDD7A.tlog\algorithm_convolution_neighborhood_square_test.lastbuildstate". The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters. [C:\pcrteam_extern\tmp\fern\fern-head-Release-prefix\src\fern-head-Release-build\source\fern\algorithm\convolution\neighborhood\test\algorithm_convolution_neighborhood_square_test.vcxproj] [C:\pcrteam_extern\tmp\fern\fern-head-Release.vcxproj]

building without tests works. with and without tests works both when using nmake makefiles