fix(backend): add missing cfg gate on mkl re-export + CBLAS-compat al… #235

Job	Run time
Pass MSRV values to other jobs	4s
nostd/thumbv6m-none-eabi/stable	37s
miri	29s
format/stable	29s
native-backend/stable	47s
cross_test/s390x-unknown-linux-gnu/stable	1m 50s
cross_test/i686-unknown-linux-gnu/stable	1m 41s
clippy/stable	36s
cargo-careful	42s
docs/nightly	2m 6s
tests/stable	1m 9s
blas-msrv	1m 1s
tests/1.64.0	1m 5s
tests/beta	1m 3s
conclusion	0s
	13m 39s

Provide feedback