Reading external Makefile variables (only) into CMake

ReadVariables.cmake

# Simple CMake utility to read variables from MK files
#   - Gets contents from given file (name or path)
#   - Parses the assignment statements
#   - Makes the same assignments in the PARENT_SCOPE

if(POLICY CMP0007)
  cmake_policy(SET CMP0007 NEW)
endif()

function(ReadVariables MKFile)
  file(READ "${MKFile}" FileContents)
  string(REPLACE "\\\n" "" FileContents ${FileContents})
  string(REPLACE "\n" ";" FileLines ${FileContents})
  list(REMOVE_ITEM FileLines "")
  foreach(line ${FileLines})
    string(REPLACE "=" ";" line_split ${line})
    list(LENGTH line_split count)
    if (count LESS 2)
      message(STATUS "Skipping ${line}")
      continue()
    endif()
    list(GET line_split -1 value)
    string(STRIP ${value} value)
    separate_arguments(value)
    list(REMOVE_AT line_split -1)
    foreach(var_name ${line_split})
      string(STRIP ${var_name} var_name)
      set(${var_name} ${value} PARENT_SCOPE)
    endforeach()
  endforeach()
endfunction()

UsageExample.cmake

# An example usage of the ReadVariables function

# Do this once in the project's top CMakeLists.txt
include(ReadVariables.cmake)

# Use the following from subdirectories as required
# CAUTION: this sets variables in the current scope (directory/function)
ReadVariables(opus_sources.mk)
message("OPUS_SOURCES: ${OPUS_SOURCES}")

Hi and thank you for your reply, I've only now got back to our CMake project where I used this function.
I've had tried to use the quotes you mentioned in line 23, but it didnt got rid of the # comment at the end of the line, so I ended up using this line right after line 23:
string(REGEX REPLACE "#.*" "" value ${value})

Which basically removes the # and everything after it on the same line, effectively ignoring comments on the line which is what I needed.
So if we got a line like this:
VAR1 = VALUE # THIS VALUE IS VERY IMPORTANT

Then string(REGEX REPLACE "#.*" "" value ${value}) will ignore the comment on the line and still take the VALUE as usual.

The 2nd one about += I ended up not using/needing as you suggested.

Thank you very much for your help!

I realize this is bringing up the dead :)

I changed the two lines for the outer for loop to
foreach(rawLine ${FileLines})
string(REGEX REPLACE "#.*" "" line ${rawLine})

Since any comment should be truncated. this way if the line is

.... # var = foo

nothing is done