CMake build script always sets `CMAKE_RANLIB` to an empty string.

[ormandi]

The cmake build script always overrides the cache value CMAKE_RANLIB with an empty string.

This is, I assume, due to the following snippet:

    # However, if no CMAKE_RANLIB was passed, pass the empty value for it explicitly,
    # as it is legacy and autodetection of ranlib made by CMake automatically
    # breaks some cross compilation builds,
    # see https://github.com/envoyproxy/envoy/pull/6991
    if not params.cache.get("CMAKE_RANLIB"):
        params.cache.update({"CMAKE_RANLIB": ""})

As far as I can tell, the condition of this if-statement always evaluates to True since as params.cache is built the item corresponding to the key CMAKE_RANLIB is popped (i.e. removed) if it was present (here) and naturally evaluates to True if the mentioned key was not present at all.

I assume to fix this one need to do basically do two things:

• Check the condition of the if-statement based on the input variable user_cache which stores the cache entries as they are taken
• And put the original value back into params.cache from user_cache if it is present. I.e. something like this:

  
  diff --git a/foreign_cc/private/cmake_script.bzl b/foreign_cc/private/cmake_script.bzl
  index bfe21bd..b4410ee 100644
  --- a/foreign_cc/private/cmake_script.bzl
  +++ b/foreign_cc/private/cmake_script.bzl
  @@ -113,8 +113,15 @@ def create_cmake_script(
   # as it is legacy and autodetection of ranlib made by CMake automatically
   # breaks some cross compilation builds,
   # see https://github.com/envoyproxy/envoy/pull/6991

• if not params.cache.get("CMAKE_RANLIB"):

• We do this by checking the key in user_cache since from params.cache

• this value is moved even if it was present before by the following call:

• https://github.com/bazelbuild/rules_foreign_cc/blob/99d018f0592bd7de492cbc2fa5e44828aea1ef4c/foreign_cc/private/cmake_script.bzl#L290

• Additionally, we also put the original value back if it got removed by

• previously.

• if not user_cache.get("CMAKE_RANLIB"): params.cache.update({"CMAKE_RANLIB": ""})
• else:

• params.cache.update({"CMAKE_RANLIB": user_cache.get("CMAKE_RANLIB")})

  Avoid CMake passing the wrong linker flags when cross compiling

  by setting CMAKE_SYSTEM_NAME and CMAKE_SYSTEM_PROCESSOR,