Disable LTO for stm32l0/lora-discovery

[danbev]

This commit suggest temporarily disabling LTO for
stm32l0/lora-discovery as it currently fails to build and produces the
following error:

$ cargo b --release
   Compiling drogue-device v0.1.0 (/home/danielbevenius/work/drougue/drogue-device/device)
   Compiling drogue-lorawan-app v0.1.0 (/home/danielbevenius/work/drougue/drogue-device/examples/apps/lorawan)
   Compiling lora-discovery v0.1.0 (/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery)
error: linking with `rust-lld` failed: exit status: 1
  |
  = note: "rust-lld" "-flavor" "gnu" "/tmp/rustcE0o7dO/symbols.o" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/deps/lora_discovery-121397784992859f.lora_discovery.44cd7467-cgu.0.rcgu.o" "--as-needed" "-L" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/deps" "-L" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/release/deps" "-L" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/build/cortex-m-e6b764a750418f37/out" "-L" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/build/cortex-m-rt-25cd07c968480796/out" "-L" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/build/defmt-c9d88f9f0247898b/out" "-L" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/build/stm32-metapac-79ebc769f1fe4173/out/src/chips/stm32l072cz" "-L" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/build/stm32-metapac-79ebc769f1fe4173/out/src/chips/stm32l072cz/memory_x/" "-L" "/home/danielbevenius/.rustup/toolchains/nightly-2022-05-24-x86_64-unknown-linux-gnu/lib/rustlib/thumbv6m-none-eabi/lib" "-Bstatic" "/tmp/rustcE0o7dO/libcortex_m_rt-83f9336232275dfb.rlib" "--start-group" "/tmp/rustcE0o7dO/libcortex_m-99a7722181c20220.rlib" "--end-group" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/deps/libcompiler_builtins-6326b44316fd805a.rlib" "-Bdynamic" "--eh-frame-hdr" "-znoexecstack" "-L" "/home/danielbevenius/.rustup/toolchains/nightly-2022-05-24-x86_64-unknown-linux-gnu/lib/rustlib/thumbv6m-none-eabi/lib" "-o" "/home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/deps/lora_discovery-121397784992859f" "--gc-sections" "--nmagic" "-Tlink.x" "-Tdefmt.x"
  = note: rust-lld: error: undefined symbol: core::intrinsics::const_eval_select::hbf83374ba4cb02aa
          >>> referenced by f64.rs:934 (/home/danielbevenius/.rustup/toolchains/nightly-2022-05-24-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/num/f64.rs:934)
          >>>               compiler_builtins-6326b44316fd805a.compiler_builtins.42fdec05-cgu.0.rcgu.o:(compiler_builtins::float::cmp::cmp::hf7fe6cc7136cc059) in archive /home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/deps/libcompiler_builtins-6326b44316fd805a.rlib
          >>> referenced by f64.rs:934 (/home/danielbevenius/.rustup/toolchains/nightly-2022-05-24-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/num/f64.rs:934)
          >>>               compiler_builtins-6326b44316fd805a.compiler_builtins.42fdec05-cgu.0.rcgu.o:(compiler_builtins::float::cmp::cmp::hf7fe6cc7136cc059) in archive /home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/deps/libcompiler_builtins-6326b44316fd805a.rlib
          >>> referenced by f64.rs:934 (/home/danielbevenius/.rustup/toolchains/nightly-2022-05-24-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/num/f64.rs:934)
          >>>               compiler_builtins-6326b44316fd805a.compiler_builtins.42fdec05-cgu.0.rcgu.o:(compiler_builtins::float::cmp::cmp::hf7fe6cc7136cc059) in archive /home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/deps/libcompiler_builtins-6326b44316fd805a.rlib
          >>> referenced 11 more times

          rust-lld: error: undefined symbol: core::intrinsics::const_eval_select::h4c3f1d9ac29a50b4
          >>> referenced by f64.rs:1027 (/home/danielbevenius/.rustup/toolchains/nightly-2022-05-24-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/num/f64.rs:1027)
          >>>               compiler_builtins-6326b44316fd805a.compiler_builtins.42fdec05-cgu.0.rcgu.o:(compiler_builtins::float::conv::__floatunsidf::hf57927b41d126d62) in archive /home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/deps/libcompiler_builtins-6326b44316fd805a.rlib
          >>> referenced by uint_macros.rs:0 (/home/danielbevenius/.rustup/toolchains/nightly-2022-05-24-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/num/uint_macros.rs:0)
          >>>               compiler_builtins-6326b44316fd805a.compiler_builtins.42fdec05-cgu.0.rcgu.o:(compiler_builtins::float::div::__divdf3::h3f7dd1a712655361) in archive /home/danielbevenius/work/drougue/drogue-device/examples/stm32l0/lora-discovery/target/thumbv6m-none-eabi/release/deps/libcompiler_builtins-6326b44316fd805a.rlib

error: could not compile `lora-discovery` due to previous error

I found the following open issue which looks like it is related:
rust-lang/rust#96486

[lulf]

Thanks!