Fix Android compilation

1. Define GIT_VERSION preprocessor variable in jni/Android.mk

   error: use of undeclared identifier 'GIT_VERSION'

2. Add -llog linker dependency for Android logging functions

   error: undefined reference to '__android_log_print'

3. Prevent Clang error providing explicit "%s" format for snprintf

   error: format string is not a string literal

libretro/libretro-core.c

@@ -156,7 +156,7 @@ static void update_variables(void)
    {
       char *pch;
       char str[100];
-      snprintf(str, sizeof(str), var.value);
+      snprintf(str, sizeof(str), "%s", var.value);
 
       pch = strtok(str, "x");
       if (pch)