NVCC flags support for mistralrs_core build

[EricLBuehler]

Support for the CUDA_NVCC_FLAGS flag. Refs #395.

[github-actions]

Code Metrics Report

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 Language            Files        Lines         Code     Comments       Blanks
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 Dockerfile              1           34           25            0            9
 Happy                   1          442          369            0           73
 JSON                    9           21           21            0            0
 Python                 32         1256         1075           37          144
 TOML                   16          444          403            1           40
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 Jupyter Notebooks       1            0            0            0            0
 |- Markdown             1           60           30           22            8
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 (Total)                            156          117           23           16
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 Markdown               18         1318            0          980          338
 |- BASH                 5          100           97            0            3
 |- Python               6          122          110            0           12
 |- Rust                 3          151          135            6           10
 (Total)                           1691          342          986          363
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 Rust                  119        36394        32883          646         2865
 |- Markdown            59          663           13          613           37
 (Total)                          37057        32896         1259         2902
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 Total                 198        39909        34776         1664         3469
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