compilation error

I got a compilation error when building with gcc 5.5 and cuda 8. Please find the config info and build error below.

```
configuring
building
/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/dyNET-2.0.3/build /tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/dyNET-2.0.3
-- The C compiler identification is GNU 5.5.0
-- The CXX compiler identification is GNU 5.5.0
-- Check for working C compiler: /nix/store/qcjlk0hnb6lysz8qshn1pc5xg51pi8p0-gcc-wrapper-5.5.0/bin/gcc
-- Check for working C compiler: /nix/store/qcjlk0hnb6lysz8qshn1pc5xg51pi8p0-gcc-wrapper-5.5.0/bin/gcc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /nix/store/qcjlk0hnb6lysz8qshn1pc5xg51pi8p0-gcc-wrapper-5.5.0/bin/g++
-- Check for working CXX compiler: /nix/store/qcjlk0hnb6lysz8qshn1pc5xg51pi8p0-gcc-wrapper-5.5.0/bin/g++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- BACKEND: cuda
/nix/store/fcxliihmhm2ak9z4890gk0qw63zsbrcx-bash-4.4-p12/bin/bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Looking for pthread_create
-- Looking for pthread_create - not found
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
-- Found CUDA: /nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit (found version "8.0")
CUDA_LIBRARIES: /nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64/libcudart_static.a;-lpthread;dl;/nix/store/27b2hylj1sv682iqijq3g7mbcfiy1rfw-glibc-2.26-131/lib/librt.so;/nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64/libcurand.so
-- Found CUDNN (include: /nix/store/vcym3d9d04w4qiq81myk4hqfydzyq454-cudatoolkit-8.0-cudnn-6.0/include, library: /nix/store/vcym3d9d04w4qiq81myk4hqfydzyq454-cudatoolkit-8.0-cudnn-6.0/lib/libcudnn.so)
-- Successfully include CUDNN flags
-- Eigen dir is /tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/eigen-eigen-2355b229ea4c
-- Found Cython version 0.27.3

--- CUDA: CUBLAS: /nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64/libcublas.so;/nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64/libcublas_device.a RT: /nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64/libcudart_static.a;dl;/nix/store/27b2hylj1sv682iqijq3g7mbcfiy1rfw-glibc-2.26-131/lib/librt.so;/nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64/libcurand.so;/nix/store/vcym3d9d04w4qiq81myk4hqfydzyq454-cudatoolkit-8.0-cudnn-6.0/lib/libcudnn.so
CMAKE_INSTALL_PREFIX="/var/empty/local"
PROJECT_SOURCE_DIR="/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/dyNET-2.0.3"
PROJECT_BINARY_DIR="/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/dyNET-2.0.3/build"
LIBS="/nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64/libcudart_static.a\;dl\;/nix/store/27b2hylj1sv682iqijq3g7mbcfiy1rfw-glibc-2.26-131/lib/librt.so\;/nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64/libcurand.so\;-lpthread"
EIGEN3_INCLUDE_DIR="/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/eigen-eigen-2355b229ea4c"
MKL_LINK_DIRS=""
WITH_CUDA_BACKEND="1"
CUDA_RT_FILES="libcudart_static.a\;dl\;librt.so\;libcurand.so\;libcudnn.so"
CUDA_RT_DIRS="/nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64\;/nix/store/27b2hylj1sv682iqijq3g7mbcfiy1rfw-glibc-2.26-131/lib\;/nix/store/vcym3d9d04w4qiq81myk4hqfydzyq454-cudatoolkit-8.0-cudnn-6.0/lib"
CUDA_CUBLAS_FILES="libcublas.so\;libcublas_device.a"
CUDA_CUBLAS_DIRS="/nix/store/rfagrp9i62gsisfcy1w5575byv9n4hb9-cudatoolkit-8.0.61-unsplit/lib64"
MSVC=""
```

Compilation fails with the following:

```
92 errors detected in the compilation of "/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/tmpxft_000006b1_00000000-15_gpu-merge3.compute_52.cpp1.ii".
CMake Error at dynet_generated_gpu-merge3.cu.o.Release.cmake:275 (message):
Error generating file
/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/dyNET-2.0.3/build/dynet/CMakeFiles/dynet.dir//./dynet_generated_gpu-merge3.cu.o

make[2]: *** [dynet/CMakeFiles/dynet.dir/build.make:100: dynet/CMakeFiles/dynet.dir/dynet_generated_gpu-merge3.cu.o] Error 1
92 errors detected in the compilation of "/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/tmpxft_00000672_00000000-15_gpu-merge1.compute_52.cpp1.ii".
CMake Error at dynet_generated_gpu-merge1.cu.o.Release.cmake:275 (message):
Error generating file
/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/dyNET-2.0.3/build/dynet/CMakeFiles/dynet.dir//./dynet_generated_gpu-merge1.cu.o

make[2]: *** [dynet/CMakeFiles/dynet.dir/build.make:86: dynet/CMakeFiles/dynet.dir/dynet_generated_gpu-merge1.cu.o] Error 1
92 errors detected in the compilation of "/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/tmpxft_0000069f_00000000-15_gpu-merge0.compute_52.cpp1.ii".
CMake Error at dynet_generated_gpu-merge0.cu.o.Release.cmake:275 (message):
Error generating file
/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/dyNET-2.0.3/build/dynet/CMakeFiles/dynet.dir//./dynet_generated_gpu-merge0.cu.o

make[2]: *** [dynet/CMakeFiles/dynet.dir/build.make:79: dynet/CMakeFiles/dynet.dir/dynet_generated_gpu-merge0.cu.o] Error 1
92 errors detected in the compilation of "/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/tmpxft_0000068e_00000000-15_gpu-merge2.compute_52.cpp1.ii".
CMake Error at dynet_generated_gpu-merge2.cu.o.Release.cmake:275 (message):
Error generating file
/tmp/nix-build-python3.6-dyNET-2.0.3.drv-0/dyNET-2.0.3/build/dynet/CMakeFiles/dynet.dir//./dynet_generated_gpu-merge2.cu.o

make[2]: *** [dynet/CMakeFiles/dynet.dir/build.make:93: dynet/CMakeFiles/dynet.dir/dynet_generated_gpu-merge2.cu.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:85: dynet/CMakeFiles/dynet.dir/all] Error 2
make: *** [Makefile:130: all] Error 2
builder for ‘/nix/store/415575yc9bi5kr4irlkjvv9s99qw44al-python3.6-dyNET-2.0.3.drv’ failed with exit code 2
cannot build derivation ‘/nix/store/vji4wa006m407pbjpdxwfjkvvsxchb8p-python3-3.6.4-env.drv’: 1 dependencies couldn't be built
```

Start by reproducing the CUDA build with the reported GCC 5.5 and CUDA 8 configuration, then inspect the generated dynet_generated_gpu-merge*.cu.o build targets and the full compiler diagnostics preceding the 92-error summaries. Done means identifying a reproducible compatibility cause and confirming that the CUDA backend builds successfully with an appropriate configuration.

Written by the indexing model from the issue text.