I am building XGBoost with GPU support on Ubuntu 18.04 following the [installation guide](https://xgboost.readthedocs.io/en/latest/build.html#building-with-gpu-support). At the stage `cmake .. -DUSE_CUDA=ON` it fails with `make[1]: execvp: /usr/local/cuda/bin: Permission denied`.

The full output is below.

```
-- CMake version 3.17.1
-- xgboost VERSION: 1.2.0
-- Configured CUDA host compiler: /usr/bin/c++
-- The CUDA compiler identification is unknown
-- Check for working CUDA compiler: /usr/local/cuda/bin
-- Check for working CUDA compiler: /usr/local/cuda/bin - broken
CMake Error at /usr/local/share/cmake-3.17/Modules/CMakeTestCUDACompiler.cmake:46 (message):
  The CUDA compiler

    "/usr/local/cuda/bin"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: /home/tassadar/lib/xgboost/build/CMakeFiles/CMakeTmp

    Run Build Command(s):/usr/bin/make cmTC_2db63/fast && /usr/bin/make  -f CMakeFiles/cmTC_2db63.dir/build.make CMakeFiles/cmTC_2db63.dir/build
    make[1]: Entering directory '/home/tassadar/lib/xgboost/build/CMakeFiles/CMakeTmp'
    Building CUDA object CMakeFiles/cmTC_2db63.dir/main.cu.o
    /usr/local/cuda/bin  -ccbin=/usr/bin/c++    -x cu -c /home/tassadar/lib/xgboost/build/CMakeFiles/CMakeTmp/main.cu -o CMakeFiles/cmTC_2db63.dir/main.cu.o
    make[1]: execvp: /usr/local/cuda/bin: Permission denied
    CMakeFiles/cmTC_2db63.dir/build.make:85: recipe for target 'CMakeFiles/cmTC_2db63.dir/main.cu.o' failed
    make[1]: *** [CMakeFiles/cmTC_2db63.dir/main.cu.o] Error 127
    make[1]: Leaving directory '/home/tassadar/lib/xgboost/build/CMakeFiles/CMakeTmp'
    Makefile:141: recipe for target 'cmTC_2db63/fast' failed
    make: *** [cmTC_2db63/fast] Error 2

  CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
  CMakeLists.txt:95 (enable_language)

-- Configuring incomplete, errors occurred!
See also "/home/tassadar/lib/xgboost/build/CMakeFiles/CMakeOutput.log".
See also "/home/tassadar/lib/xgboost/build/CMakeFiles/CMakeError.log".

```

The permissions of `/usr/local/cuda/bin` are as follows.

```
total 59288
drwxrwxrwx  3 tassadar tassadar     4096 чер  4 15:55 .
drwxr-xr-x 18 root     root         4096 чер  4 15:55 ..
-rwxrwxrwx  1 root     root        80576 чер  4 15:55 bin2c
lrwxrwxrwx  1 root     root            4 чер  4 15:55 computeprof -> nvvp
drwxrwxrwx  2 root     root         4096 чер  4 15:55 crt
-rwxrwxrwx  1 root     root      4833904 чер  4 15:55 cudafe++
-rwxrwxrwx  1 root     root      8890248 чер  4 15:55 cuda-gdb
-rwxrwxrwx  1 root     root       581744 чер  4 15:55 cuda-gdbserver
-rwxrwxrwx  1 root     root          800 чер  4 15:55 cuda-install-samples-10.2.sh
-rwxrwxrwx  1 root     root       397480 чер  4 15:55 cuda-memcheck
-rwxrwxrwx  1 root     root       931664 чер  4 15:55 cuda-uninstaller
-rwxrwxrwx  1 root     root       212224 чер  4 15:55 cuobjdump
-rwxrwxrwx  1 root     root       195600 чер  4 15:55 fatbinary
-rwxrwxrwx  1 root     root          219 чер  4 15:55 nsight
-rwxrwxrwx  1 root     root         1580 чер  4 15:55 nsight_ee_plugins_manage.sh
-rwxrwxrwx  1 root     root          444 чер  4 15:55 nsight-sys
-rwxrwxrwx  1 root     root          512 чер  4 15:55 nsys
-rwxrwxrwx  1 root     root          533 чер  4 15:55 nsys-exporter
-rwxrwxrwx  1 root     root       229504 чер  4 15:55 nvcc
-rwxrwxrwx  1 root     root          417 чер  4 15:55 nvcc.profile
-rwxrwxrwx  1 root     root     23034280 чер  4 15:55 nvdisasm
-rwxrwxrwx  1 root     root      8092008 чер  4 15:55 nvlink
-rwxrwxrwx  1 root     root         2583 чер  4 15:55 nv-nsight-cu
-rwxrwxrwx  1 root     root         2801 чер  4 15:55 nv-nsight-cu-cli
-rwxrwxrwx  1 root     root      5094688 чер  4 15:55 nvprof
-rwxrwxrwx  1 root     root        97168 чер  4 15:55 nvprune
-rwxrwxrwx  1 root     root          285 чер  4 15:55 nvvp
-rwxrwxrwx  1 root     root      7955808 чер  4 15:55 ptxas

```

What am I doing wrong?