move build stuff to build dir #77

Job	Run time
coverage - measure	1m 28s
sanitizer - arm64v8/debian:bookworm	2m 0s
sanitizer - debian:bookworm	1m 1s
msys2 - mingw32	2m 28s
sanitizer - arm32v7/debian:bookworm	1m 59s
msys2 - mingw64	2m 35s
macosx	2m 27s
linux - arm64v8/debian:bookworm	2m 32s
linux - debian:bookworm	58s
linux - ubuntu:noble	1m 30s
linux - arm32v7/debian:bookworm	2m 39s
	21m 37s

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