Use fp32 in cuBLAS V100 to avoid overflows, env variables to override cuBLAS compute...

Use fp32 in cuBLAS V100 to avoid overflows, env variables to override cuBLAS compute type (llama/19959)

* Update ggml-cuda.cu

* Update ggml-cuda.cu

* Update build.md

* Update build.md

* Update ggml/src/ggml-cuda/ggml-cuda.cu

Co-authored-by: Johannes Gäßler <redacted>
* Update ggml-cuda.cu

* Update build.md

* Update ggml/src/ggml-cuda/ggml-cuda.cu

Co-authored-by: Johannes Gäßler <redacted>
* Update build.md

* Update ggml-cuda.cu

* Update ggml-cuda.cu

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Co-authored-by: Johannes Gäßler <redacted>