-Z build-std builds a "no op" std for the target, even no-std ones
that won't work for ARMv6-M because std depends on CAS and that target
lacks CAS
ARMv7-M also has problems with recent nightlies due to
rust-lang/rust#98378
this commit changes the logic to use a smaller -Z build-std=alloc
subset for no-std targets
targets are considered 'no-std' when rustc --print=cfg --target $T
reports target_os="none"
fixes #55
-Z build-stdbuilds a "no op" std for the target, even no-std ones that won't work for ARMv6-M because std depends on CAS and that target lacks CAS ARMv7-M also has problems with recent nightlies due to rust-lang/rust#98378this commit changes the logic to use a smaller
-Z build-std=allocsubset for no-std targets targets are considered 'no-std' whenrustc --print=cfg --target $Treportstarget_os="none"