move build stuff to build dir #251

Job	Run time
macosx	2m 14s
sanitizer - arm32v7/debian:bookworm	3m 14s
coverage - measure	2m 13s
sanitizer - arm64v8/debian:bookworm	2m 50s
sanitizer - debian:bookworm	1m 40s
linux - debian:bookworm	1m 53s
linux - ubuntu:noble	1m 42s
linux - arm32v7/debian:bookworm	3m 3s
conan - macos-latest	1m 27s
linux - arm64v8/debian:bookworm	3m 24s
conan - linux \|	2m 5s
msys2 - mingw64	2m 32s
android	6m 17s
msys2 - mingw32	2m 50s
conan - emscripten \|	2m 8s
msvs	4m 9s
ios	55s
vcpkg - linux \|	1m 52s
vcpkg - windows	3m 23s
	49m 51s

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