Reduce binary size.

[Tim-Nosco]

cargo bloat --bin tshr --target mipsel-unknown-linux-musl --profile prof output

 File  .text     Size           Crate Name
 1.2%   5.4%  28.2KiB       [Unknown] main
 1.2%   5.4%  28.2KiB             std addr2line::ResDwarf<R>::parse
 1.1%   4.8%  24.9KiB       [Unknown] _ZN9libunwind10CFI_ParserINS_17LocalAddressSpaceEE20parseFDEInstructionsERS1_RKNS2_8FDE_InfoERKNS2_8CIE_InfoEjiPNS2_10PrologInfoE
 1.0%   4.5%  23.1KiB             std std::backtrace_rs::symbolize::gimli::resolve::{{closure}}
 0.6%   2.7%  14.1KiB             std addr2line::ResUnit<R>::parse_lines
 0.4%   1.9%   9.8KiB             std miniz_oxide::inflate::core::decompress
 0.3%   1.5%   7.9KiB             std gimli::read::unit::parse_attribute
 0.3%   1.5%   7.7KiB       [Unknown] printf_core
 0.3%   1.4%   7.3KiB            p256 p256::arithmetic::scalar::Scalar::mul
 0.2%   1.1%   5.6KiB            sha2 sha2::sha256::compress256
 0.2%   1.0%   5.4KiB             std gimli::read::rnglists::RngListIter<R>::next
 0.2%   0.9%   4.8KiB             std core::slice::sort::recurse
 0.2%   0.9%   4.7KiB       [Unknown] _ZN9libunwind14EHHeaderParserINS_17LocalAddressSpaceEE7findFDEERS1_jjjPNS_10CFI_ParserIS1_E8FDE_InfoEPNS5_8CIE_InfoE
 0.2%   0.9%   4.5KiB elliptic_curve? <elliptic_curve::public_key::PublicKey<C> as alloc::string::ToString>::to_string
 0.2%   0.9%   4.4KiB            p256 p256::arithmetic::field::FieldElement::mul
 0.2%   0.8%   4.3KiB       [Unknown] _ZN9libunwind17DwarfInstructionsINS_17LocalAddressSpaceENS_18Registers_mips_o32EE18evaluateExpressionEjRS1_RKS2_j
 0.2%   0.8%   4.3KiB       rand_core <rand_core::block::BlockRng<R> as rand_core::RngCore>::fill_bytes
 0.2%   0.8%   4.2KiB             std <&T as core::fmt::Display>::fmt
 0.2%   0.8%   4.2KiB             std addr2line::function::Function<R>::parse_children
 0.2%   0.7%   3.8KiB             std gimli::read::line::parse_attribute
13.7%  61.1% 316.2KiB                 And 997 smaller methods. Use -n N to show more.
22.4% 100.0% 517.9KiB                 .text section size, the file size is 2.3MiB
```'

Potentially removing `addr2line` can reduce space.

[Tim-Nosco]

Maybe use conditional code to remove debugging strings/prints/formats. Potentially condition on cfg(debug_assert)
Find occurrences of format! and rework.

[Tim-Nosco]

Turns out, the build was not working as expected:

diff --git a/.cargo/config b/.cargo/config
index 5f1300e..6610cd3 100644
--- a/.cargo/config
+++ b/.cargo/config
@@ -5,6 +5,6 @@ linker = "mipsel-buildroot-linux-uclibc-gcc"
 linker = "mipsel-linux-musl-cross/bin/mipsel-linux-musl-gcc"
 rustflags = ["-Ctarget-feature=+crt-static"]

-[target.mipsel-unknown-linux-musl.unstable]
-build-std = "std,core,alloc,panic_abort"
-build-std-features = "panic_immediate_abort"
+[unstable]
+build-std = ["std","core","alloc","panic_abort"]
+build-std-features = ["panic_immediate_abort"]

These two versions do not perform the same way.

[Tim-Nosco]

./scripts/bloat.sh
    Finished bloat [optimized] target(s) in 0.04s
    Analyzing target/mipsel-unknown-linux-musl/bloat/tshr

 File  .text     Size           Crate Name
 6.8%  14.6%  26.4KiB       [Unknown] main
 1.9%   4.1%   7.3KiB            p256 p256::arithmetic::scalar::Scalar::mul
 1.6%   3.4%   6.2KiB            sha2 sha2::sha256::compress256
 1.1%   2.5%   4.4KiB            p256 p256::arithmetic::field::FieldElement::mul
 1.1%   2.3%   4.2KiB elliptic_curve? <elliptic_curve::public_key::PublicKey<C> as alloc::string::ToString>::to_string
 1.0%   2.2%   4.0KiB       rand_core <rand_core::block::BlockRng<R> as rand_core::RngCore>::fill_bytes
 0.7%   1.5%   2.7KiB             aes aes::soft::fixslice::aes256_encrypt
 0.6%   1.4%   2.4KiB  universal_hash universal_hash::UniversalHash::update
 0.6%   1.3%   2.4KiB     pem_rfc7468 base64ct::decoder::Decoder<E>::perform_decode
 0.5%   1.1%   2.1KiB            p256 p256::arithmetic::projective::ProjectivePoint::add
 0.5%   1.1%   1.9KiB       [Unknown] malloc
 0.4%   1.0%   1.7KiB            core <str as core::fmt::Debug>::fmt
 0.4%   0.9%   1.6KiB       [Unknown] __bin_chunk
 0.4%   0.9%   1.6KiB   crypto_common crypto_common::KeyInit::new_from_slice
 0.4%   0.8%   1.5KiB             std <std::io::error::ErrorKind as core::fmt::Debug>::fmt
 0.4%   0.8%   1.5KiB            p256 p256::arithmetic::projective::ProjectivePoint::double
 0.4%   0.8%   1.4KiB     pem_rfc7468 <T as base64ct::encoding::Encoding>::decode
 0.3%   0.7%   1.2KiB            p256 p256::arithmetic::field::FieldElement::montgomery_reduce
 0.3%   0.7%   1.2KiB     pem_rfc7468 <T as base64ct::encoding::Encoding>::encode
 0.3%   0.7%   1.2KiB       [Unknown] memcpy
26.5%  57.4% 103.7KiB                 And 568 smaller methods. Use -n N to show more.
46.2% 100.0% 180.7KiB                 .text section size, the file size is 391.3KiB

[Tim-Nosco]

rust-lang/cargo#8733