android: enable custom (e)println output via android log system (#8135)

examples/2048/2048.v

@@ -936,13 +936,6 @@ fn (mut app App) showfps() {
 	}
 }
 
-// TODO: Move this somewhere else (vlib?) once Android support is merged
-$if android {
-	#include <android/log.h>
-	#define LOG_TAG "v_logcat_test"
-	#define printf(...) __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
-	#define fprintf(a, ...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
-}
 fn main() {
 	mut app := &App{}
 	app.new_game()

thirdparty/sokol/sokol_v.h

@@ -0,0 +1,20 @@
+#if defined(__ANDROID__)
+	// Adapted from https://stackoverflow.com/a/196018/1904615
+	#define V_ANDROID_LOG_STR_VALUE(arg) #arg
+	#define V_ANDROID_LOG_NAME(tag_name) V_ANDROID_LOG_STR_VALUE(tag_name)
+
+	#ifndef V_ANDROID_LOG_TAG
+		#if defined(APPNAME)
+			#define V_ANDROID_LOG_TAG APPNAME
+		#else
+			#define V_ANDROID_LOG_TAG "V_ANDROID"
+		#endif
+	#endif
+
+	#define V_ANDROID_LOG_TAG_NAME V_ANDROID_LOG_NAME(V_ANDROID_LOG_TAG)
+
+	#include <android/log.h>
+	#define printf(...) __android_log_print(ANDROID_LOG_INFO, V_ANDROID_LOG_TAG_NAME, __VA_ARGS__)
+	#define fprintf(a, ...) __android_log_print(ANDROID_LOG_ERROR, V_ANDROID_LOG_TAG_NAME, __VA_ARGS__)
+#endif
+

vlib/sokol/c/declaration.c.v

@@ -41,6 +41,8 @@ pub const (
 #flag solaris -DSOKOL_NO_ENTRY
 // TODO end
 
+#include "sokol_v.h"
+
 #include "sokol_app.h"
 
 #define SOKOL_IMPL