Fix broken LND integration test

[tnull]

Seems the new LND integration test we just added in #509 is already broken:

error: failed to run custom build command for `prost-build v0.10.4`

Caused by:
  process didn't exit successfully: `/home/runner/work/ldk-node/ldk-node/target/debug/build/prost-build-c64a445e56726d39/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-changed=/home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/prost-build-0.10.4/third-party/protobuf/cmake
  CMAKE_TOOLCHAIN_FILE_x86_64-unknown-linux-gnu = None
  CMAKE_TOOLCHAIN_FILE_x86_64_unknown_linux_gnu = None
  HOST_CMAKE_TOOLCHAIN_FILE = None
  CMAKE_TOOLCHAIN_FILE = None
  CMAKE_GENERATOR_x86_64-unknown-linux-gnu = None
  CMAKE_GENERATOR_x86_64_unknown_linux_gnu = None
  HOST_CMAKE_GENERATOR = None
  CMAKE_GENERATOR = None
  CMAKE_PREFIX_PATH_x86_64-unknown-linux-gnu = None
  CMAKE_PREFIX_PATH_x86_64_unknown_linux_gnu = None
  HOST_CMAKE_PREFIX_PATH = None
  CMAKE_PREFIX_PATH = None
  CMAKE_x86_64-unknown-linux-gnu = None
  CMAKE_x86_64_unknown_linux_gnu = None
  HOST_CMAKE = None
  CMAKE = None
  running: cd "/home/runner/work/ldk-node/ldk-node/target/debug/build/prost-build-3d489692c0137d56/out/build" && CMAKE_PREFIX_PATH="" LC_ALL="C" "cmake" "/home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/prost-build-0.10.4/third-party/protobuf/cmake" "-Dprotobuf_BUILD_TESTS=OFF" "-DCMAKE_INSTALL_PREFIX=/home/runner/work/ldk-node/ldk-node/target/debug/build/prost-build-3d489692c0137d56/out" "-DCMAKE_C_FLAGS= -ffunction-sections -fdata-sections -fPIC -m64" "-DCMAKE_C_COMPILER=/usr/bin/cc" "-DCMAKE_CXX_FLAGS= -ffunction-sections -fdata-sections -fPIC -m64" "-DCMAKE_CXX_COMPILER=/usr/bin/c++" "-DCMAKE_ASM_FLAGS= -ffunction-sections -fdata-sections -fPIC -m64" "-DCMAKE_ASM_COMPILER=/usr/bin/cc" "-DCMAKE_BUILD_TYPE=Debug"
  -- Configuring incomplete, errors occurred!

  --- stderr
  CMake Error at CMakeLists.txt:2 (cmake_minimum_required):
    Compatibility with CMake < 3.5 has been removed from CMake.

    Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
    to tell CMake that the project requires at least <min> but has been updated
    to work with policies introduced by <max> or earlier.

    Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.



  thread 'main' panicked at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/cmake-0.1.54/src/lib.rs:1119:5:

  command did not execute successfully, got: exit status: 1

  build script failed, must exit now
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

We need to fix this to unbreak CI.

[tnull]

@moisesPompilio Would you be interested in taking a look at this?

[moisesPompilio]

Yes, I’ll check it out