Audio System + Drivers (#562)

Buildscripts/properties.cmake

@@ -1,4 +1,11 @@
 function(GET_PROPERTY_VALUE PROPERTIES_CONTENT_VAR KEY_NAME RESULT_VAR)
+    # Optional 4th arg: default value returned when key is missing, instead of erroring.
+    set(has_default FALSE)
+    if (${ARGC} GREATER 3)
+        set(has_default TRUE)
+        set(default_value "${ARGV3}")
+    endif ()
+
     # Search for the key and its value in the properties content
     # Supports KEY=VALUE, KEY="VALUE", and optional spaces around =
     # Use parentheses to capture the value
@@ -6,6 +13,8 @@ function(GET_PROPERTY_VALUE PROPERTIES_CONTENT_VAR KEY_NAME RESULT_VAR)
     # So we look for the key at the beginning of the string or after a newline.
     if ("${${PROPERTIES_CONTENT_VAR}}" MATCHES "(^|\n)${KEY_NAME}[ \t]*=[ \t]*\"?([^\n\"]*)\"?")
         set(${RESULT_VAR} "${CMAKE_MATCH_2}" PARENT_SCOPE)
+    elseif (has_default)
+        set(${RESULT_VAR} "${default_value}" PARENT_SCOPE)
     else ()
         message(FATAL_ERROR "Property '${KEY_NAME}' not found in the properties content.")
     endif ()