Ensure compilation with newest architectures

[sofiemartins]

Whether compilation without specification of the architecture compiles to the newest architecture depends on the system settings. In HiRep, the user may specify the architecture in the GPUFLAGS when building, but ideally, they don't have to. There was a specific case for Tursa, where the fat binary compiled without specification of the architecture compiles only for compute capability 5.2, which causes issues with cub reductions.

This was the origin of the issue in #126

The suggestion below enforces the usage of -arch=all, but only if the user did not specify the target architecture.
I tested this by checking the build commands by eye using nj -v.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.77%. Comparing base (458b7d0) to head (547b47e).

Additional details and impacted files

@@              Coverage Diff               @@
##           HiRep-CUDA     #129      +/-   ##
==============================================
- Coverage       49.00%   48.77%   -0.23%     
==============================================
  Files             383      192     -191     
  Lines           58365    29781   -28584     
  Branches        10806     5876    -4930     
==============================================
- Hits            28602    14526   -14076     
+ Misses          26935    13792   -13143     
+ Partials         2828     1463    -1365     

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