ci: move build jobs into a separate workflow #2

Job	Run time
ESP-IDF	19s
Apple Other	1m 56s
Cross (sparcv9-sun-solaris)	27s
RDRAND (x86_64-unknown-uefi)	21s
Cross (x86_64-unknown-illumos)	37s
RNDR	28s
RDRAND (x86_64-unknown-l4re-uclibc)	22s
Cross (x86_64-unknown-freebsd)	50s
Cross (x86_64-unknown-netbsd)	40s
Tier 2 (x86_64-unknown-fuchsia)	20s
Tier 2 (x86_64-unknown-redox)	8s
Tier 3 (x86_64-unknown-hermit)	22s
Tier 2 (x86_64-fortanix-unknown-sgx)	15s
Wasm64	30s
Tier 3 (x86_64-wrs-vxworks)	25s
Tier 3 (aarch64-kmc-solid_asp3)	26s
Tier 3 (armv6k-nintendo-3ds)	19s
Tier 3 (armv7-sony-vita-newlibeabihf)	24s
Tier 3 (aarch64-unknown-nto-qnx710)	30s
Tier 3 (x86_64-unknown-openbsd, std)	30s
Tier 3 (x86_64-unknown-dragonfly, std)	29s
Tier 3 (x86_64-unknown-haiku, std)	34s
Tier 3 (i686-unknown-hurd-gnu, std)	34s
No Atomics	15s
	12m 1s

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