To get a sense of the scale despite mdevctl being so small in it's function here
the rust portion of the build-dependency tree. (Due to the way rust libs work some are from the same source - so two lists):

Maybe some of them are for dh-rust, maybe we need all of them. Since there is no full detection for built-using yet (that I'd know of) this is guessing from what I get when I run apt build-dep in an empty container.

Sources to MIR:
Source: rust-aho-corasick
Source: rust-ansi-term
Source: rust-anyhow
Source: rust-atty
Source: rust-autocfg
Source: rust-bitflags
Source: rust-cfg-if-0.1
Source: rust-clap
Source: rust-cloudabi (0.0.3-1)
Source: rust-env-logger
Source: rust-getrandom
Source: rust-heck
Source: rust-humantime
Source: rust-indexmap
Source: rust-itoa
Source: rust-lazy-static
Source: rust-libc
Source: rust-lock-api
Source: rust-log
Source: rust-memchr
Source: rust-once-cell
Source: rust-parking-lot
Source: rust-parking-lot-core
Source: rust-ppv-lite86
Source: rust-proc-macro-error
Source: rust-proc-macro-error-attr
Source: rust-proc-macro2
Source: rust-quote
Source: rust-rand
Source: rust-rand-chacha
Source: rust-rand-core
Source: rust-rand-hc (0.2.0-1)
Source: rust-redox-syscall
Source: rust-regex
Source: rust-regex-syntax
Source: rust-remove-dir-all
Source: rust-ryu
Source: rust-scopeguard
Source: rust-serde
Source: rust-serde-json
Source: rust-smallvec
Source: rust-strsim
Source: rust-structopt
Source: rust-structopt-derive
Source: rust-syn
Source: rust-syn-mid
Source: rust-tempfile
Source: rust-termcolor
Source: rust-textwrap (0.11.0-1)
Source: rust-thread-local
Source: rust-unicode-segmentation
Source: rust-unicode-width
Source: rust-unicode-xid
Source: rust-uuid
Source: rust-vec-map (0.8.1-2)
Source: rust-version-check
Source: rust-winapi
Source: rust-winapi-i686-pc-windows-gnu (0.4.0-1)
Source: rust-winapi-util
Source: rust-winapi-x86-64-pc-windows-gnu (0.4.0-1)

Effective full build-time dependencies:
librust-aho-corasick+std-dev
librust-aho-corasick-dev
librust-ansi-term-dev
librust-anyhow-dev
librust-atty-dev
librust-autocfg-dev
librust-bitflags-dev
librust-cfg-if-0.1-dev
librust-clap+color-dev
librust-clap+default-dev
librust-clap+strsim-dev
librust-clap-dev
librust-cloudabi+default-dev
librust-cloudabi-dev
librust-env-logger+default-dev
librust-env-logger-dev
librust-getrandom-dev
librust-heck-dev
librust-humantime-dev
librust-indexmap-dev
librust-itoa-dev
librust-lazy-static-dev
librust-libc-dev
librust-lock-api-dev
librust-log+serde-dev
librust-log-dev
librust-memchr-dev
librust-once-cell-dev
librust-parking-lot-core-dev
librust-parking-lot-dev
librust-ppv-lite86-dev
librust-proc-macro-error-attr-dev
librust-proc-macro-error-dev
librust-proc-macro2-dev
librust-quote+proc-macro-dev
librust-quote-dev
librust-rand+alloc-dev
librust-rand+getrandom-dev
librust-rand+std-dev
librust-rand-chacha+std-dev
librust-rand-chacha-dev
librust-rand-core+getrandom-dev
librust-rand-core+std-dev
librust-rand-core-dev
librust-rand-dev
librust-rand-hc-dev
librust-redox-syscall-dev
librust-regex+default-dev
librust-regex+perf-cache-dev
librust-regex+perf-dev
librust-regex+perf-literal-dev
librust-regex+unicode-age-dev
librust-regex+unicode-bool-dev
librust-regex+unicode-case-dev
librust-regex+unicode-dev
librust-regex+unicode-gencat-dev
librust-regex+unicode-perl-dev
librust-regex+unicode-script-dev
librust-regex+unicode-segment-dev
librust-regex-dev
librust-regex-syntax+unicode-dev
librust-regex-syntax-dev
librust-remove-dir-all-dev
librust-ryu-dev
librust-scopeguard-dev
librust-serde-dev
librust-serde-json+indexmap-dev
librust-serde-json-dev
librust-smallvec-dev
librust-strsim-dev
librust-structopt+default-dev
librust-structopt-derive-dev
librust-structopt-dev
librust-syn+default-dev
librust-syn+printing-dev
librust-syn+proc-macro-dev
librust-syn-dev
librust-syn-mid-dev
librust-tempfile-dev
librust-termcolor-dev
librust-textwrap-dev
librust-thread-local-dev
librust-unicode-segmentation-dev
librust-unicode-width-dev
librust-unicode-xid-dev
librust-uuid-dev
librust-vec-map-dev
librust-version-check-dev
librust-winapi-dev
librust-winapi-i686-pc-windows-gnu-dev
librust-winapi-util-dev
librust-winapi-x86-64-pc-windows-gnu-dev