Add VARS_TO_IGNORE

cmake/AwsGetCmdArguments.cmake

@@ -6,12 +6,22 @@
 # strings for variables provided via command line to the "No help, variable specified on the command line." phrase since
 # at least v3.0.
 # Via https://cmake.org/pipermail/cmake/2018-January/067002.html
+# Arguments:
+#  VARS_TO_IGNORE Variables that should be ignored even if they were provided via command line. Multiple variables can
+#                 be specified separated by space.
 #
 # MUST be done before call to 'project'. The reason is that project() resets help strings for some variables
 # (e.g. CMAKE_INSTALL_PREFIX).
 # 
 # Populate AWS_CMAKE_CMD_ARGS with command line variables and their values.
 function(aws_get_cmd_arguments)
+    set(multiValueArgs VARS_TO_IGNORE)
+    cmake_parse_arguments(AWS_GET_CMD_ARGS "" "" "${multiValueArgs}" ${ARGN})
+
+    if (AWS_GET_CMD_ARGS_VARS_TO_IGNORE)
+        message(STATUS "Ignored vars: ${AWS_GET_CMD_ARGS_VARS_TO_IGNORE}")
+    endif()
+
     if (PROJECT_NAME)
         message(WARNING "aws_get_cmd_arguments is called after project(), some variables may be missed")
     endif()
@@ -25,6 +35,9 @@ function(aws_get_cmd_arguments)
     foreach(var ${vars})
         get_property(currentHelpString CACHE "${var}" PROPERTY HELPSTRING)
         if ("${currentHelpString}" MATCHES "No help, variable specified on the command line.")
+            if("${var}" IN_LIST AWS_GET_CMD_ARGS_VARS_TO_IGNORE)
+                continue()
+            endif()
             set(escaped_var ${${var}})
             # To store a list within another list, it needs to be escaped first.
             string(REPLACE ";" "\\\\;" escaped_var "${${var}}")