Move WiFi credentials to variables

No more creds.c

Set PICOWOTA_WIFI_SSID/PICOWOTA_WIFI_PASS environment variables or
CMake variables.

CMakeLists.txt

 
 add_executable(picowota
 	main.c
-	creds.c
 	tcp_comm.c
 )
 
 	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 ()
+
+if (DEFINED ENV{PICOWOTA_WIFI_PASS} AND (NOT PICOWOTA_WIFI_PASS))
+	set(PICOWOTA_WIFI_PASS $ENV{PICOWOTA_WIFI_PASS})
+	message("Using PICOWOTA_WIFI_PASS from environment (hidden)")
+endif ()
+
+if ((NOT PICOWOTA_WIFI_SSID) OR (NOT PICOWOTA_WIFI_PASS))
+        message(FATAL_ERROR
+		"WiFi SSID/Pass not set, please set PICOWOTA_WIFI_SSID/PICOWOTA_WIFI_PASS."
+	)
+endif ()
+
+# TODO: This causes a full rebuild if they change, configure_file might
+# be better.
+target_compile_definitions(picowota PUBLIC PICOWOTA_WIFI_SSID=${PICOWOTA_WIFI_SSID})
+target_compile_definitions(picowota PUBLIC PICOWOTA_WIFI_PASS=${PICOWOTA_WIFI_PASS})
+
 # Provide a helper to build a standalone target
 function(picowota_build_standalone NAME)
 	get_target_property(PICOWOTA_SRC_DIR picowota SOURCE_DIR)

creds.c

-const char *wifi_ssid = "YourNetworkName";
-const char *wifi_pass = "YourPassw0rd";

main.c

 #define DBG_PRINTF(...) { }
 #endif
 
-extern const char *wifi_ssid;
-extern const char *wifi_pass;
+#define QUOTE(name) #name
+#define STR(macro) QUOTE(macro)
+
+#ifndef PICOWOTA_WIFI_SSID
+#warning "PICOWOTA_WIFI_SSID not defined"
+#else
+const char *wifi_ssid = STR(PICOWOTA_WIFI_SSID);
+#endif
+
+#ifndef PICOWOTA_WIFI_PASS
+#warning "PICOWOTA_WIFI_PASS not defined"
+#else
+const char *wifi_pass = STR(PICOWOTA_WIFI_PASS);
+#endif
+
 critical_section_t critical_section;
 
 #define EVENT_QUEUE_LENGTH 8