Merge pull request #1223 from lightning-signer/2021-12-invoice-nostd

Adapt lightning-invoice to no_std

diff --cc .github/workflows/build.yml
index 9b4621e470fff039c4d76faaa29167e179e3c59b,5dcbb677e6d8a6d6f88e62b20e7307c862807c0e..002005f1809ef32adbb464a9a5491383512a0dbd
--- 1/.github/workflows/build.yml
--- 2/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@@ -115,9 -114,12 +115,14 @@@ jobs
            cargo test --verbose --color always --no-default-features --features no-std
            # check if there is a conflict between no-std and the default std feature
            cargo test --verbose --color always --features no-std
 +          # check if there is a conflict between no-std and the c_bindings cfg
 +          RUSTFLAGS="--cfg=c_bindings" cargo test --verbose --color always --no-default-features --features=no-std
            cd ..
+           cd lightning-invoice
+           cargo test --verbose --color always --no-default-features --features no-std
+           # check if there is a conflict between no-std and the default std feature
+           cargo test --verbose --color always --features no-std
+           cd ..
        - name: Test on no-std builds Rust ${{ matrix.toolchain }} and full code-linking for coverage generation
          if: "matrix.build-no-std && matrix.coverage"
          run: |