Add cmake option to select asn1c, and test asn1c parameters

CMake now takes the option ASN1C_EXEC to select an asn1c to use for
compilation. For instance, run with
cmake .. -GNinja -DASN1C_EXEC=/opt/asn1c/bin/asn1c
or
./build_oai --cmake-opt -DASN1C_EXEC=/opt/asn1c/bin/asn1c
to select the alternative asn1c. For instance, this is important for the
CI to allow to build multiple versions of OAI in parallel that might use
different commits of OAI.

Further, this patch introduces functionality to check for the support of
asn1c options that we require, and alerts the user if they are missing,
alongside a message of how to resolve the problem.

cmake_targets/macros.cmake

@@ -89,3 +89,21 @@ macro(eval_boolean VARIABLE)
     set(${VARIABLE} OFF)
   endif()
 endmacro()
+
+function(check_option EXEC TEST_OPTION EXEC_HINT)
+  message(STATUS "Check if ${EXEC} supports ${TEST_OPTION}")
+  execute_process(COMMAND ${EXEC} ${TEST_OPTION}
+                  RESULT_VARIABLE CHECK_STATUS
+                  OUTPUT_VARIABLE CHECK_OUTPUT
+                  ERROR_VARIABLE CHECK_OUTPUT)
+  if(NOT ${CHECK_STATUS} EQUAL 1)
+    get_filename_component(EXEC_FILE ${EXEC} NAME)
+    message(FATAL_ERROR "Error message: ${CHECK_OUTPUT}\
+You might want to re-run ./build_oai -I
+Or provide a path to ${EXEC_FILE} using
+  ./build_oai ... --cmake-opt -D${EXEC_HINT}=/path/to/${EXEC_FILE}
+or directly with
+  cmake .. -D${EXEC_HINT}=/path/to/${EXEC_FILE}
+")
+  endif()
+endfunction()