Allow defining PICOWOTA_WIFI_AP in the environment

This aligns the behavior of the build variables, providing a helper function to do the job.

CMakeLists.txt

@@ -73,15 +73,22 @@ target_link_libraries(picowota
 	picowota_reboot
 )
 
-if (DEFINED ENV{PICOWOTA_WIFI_SSID} AND (NOT PICOWOTA_WIFI_SSID))
-	set(PICOWOTA_WIFI_SSID $ENV{PICOWOTA_WIFI_SSID})
-	message("Using PICOWOTA_WIFI_SSID from environment ('${PICOWOTA_WIFI_SSID}')")
-endif ()
+# Retrieves build variables from the environment if present
+function(picowota_retrieve_variable name hidden)
+	if (DEFINED ENV{${name}} AND (NOT ${name}))
+		set(${name} $ENV{${name}} PARENT_SCOPE)
+		if (hidden)
+			set(log_value "hidden")
+		else()
+			set(log_value "'$ENV{${name}}'")
+		endif()
+		message("Using ${name} from environment (${log_value})")
+	endif()
+endfunction()
 
-if (DEFINED ENV{PICOWOTA_WIFI_PASS} AND (NOT PICOWOTA_WIFI_PASS))
-	set(PICOWOTA_WIFI_PASS $ENV{PICOWOTA_WIFI_PASS})
-	message("Using PICOWOTA_WIFI_PASS from environment (hidden)")
-endif ()
+picowota_retrieve_variable(PICOWOTA_WIFI_SSID false)
+picowota_retrieve_variable(PICOWOTA_WIFI_PASS true)
+picowota_retrieve_variable(PICOWOTA_WIFI_AP false)
 
 if ((NOT PICOWOTA_WIFI_SSID) OR (NOT PICOWOTA_WIFI_PASS))
         message(FATAL_ERROR