build

SPQR: Make GPUQREngine and SuiteSparse_GPURuntime subprojects #464

Job	Run time
macos	45m 3s
ubuntu (gcc with CUDA with OpenMP)	5m 32s
ubuntu (gcc without CUDA with OpenMP)	3m 29s
ubuntu (clang with CUDA with OpenMP)	5m 40s
ubuntu (clang without CUDA with OpenMP)	3m 45s
msvc (with OpenMP)	6m 50s
ubuntu (gcc without CUDA without OpenMP)	3m 16s
mingw (MINGW64)	8m 2s
msvc (without OpenMP)	7m 53s
mingw (MINGW32)	8m 33s
mingw (CLANG64)	10m 53s
mingw (CLANG32)	8m 45s
	1h 57m 41s

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