Fix Ruby 2.7 rb_check_safe_obj warnings

Author: byroot

ext/sqlite3/database.c

@@ -40,11 +40,13 @@ static VALUE rb_sqlite3_open_v2(VALUE self, VALUE file, VALUE mode, VALUE zvfs)
 
   Data_Get_Struct(self, sqlite3Ruby, ctx);
 
+#if defined TAINTING_SUPPORT
 #if defined StringValueCStr
   StringValuePtr(file);
   rb_check_safe_obj(file);
 #else
   Check_SafeStr(file);
+#endif
 #endif
 
       status = sqlite3_open_v2(
@@ -761,11 +763,13 @@ static VALUE rb_sqlite3_open16(VALUE self, VALUE file)
 
   Data_Get_Struct(self, sqlite3Ruby, ctx);
 
+#if defined TAINTING_SUPPORT
 #if defined StringValueCStr
   StringValuePtr(file);
   rb_check_safe_obj(file);
 #else
   Check_SafeStr(file);
+#endif
 #endif
 
   status = sqlite3_open16(utf16_string_value_ptr(file), &ctx->db);

ext/sqlite3/extconf.rb

@@ -47,6 +47,10 @@
   $CFLAGS << ' -W3'
 end
 
+if RUBY_VERSION < '2.7'
+  $CFLAGS << ' -DTAINTING_SUPPORT'
+end
+
 def asplode missing
   if RUBY_PLATFORM =~ /mingw|mswin/
     abort "#{missing} is missing. Install SQLite3 from " +