Why is the Arduino IDE ignoring my replacement start up code? I am trying to replace the standard startup code to save flash space. 

I've put the new startup.s in my core directory and added the -nostartfiles parameter to the linker reciepe in my platform.txt. 

When I compile with the IDE, it does not include my start code at all. 

When I use Atmel Studio or a makefile, the code assembles and is included just fine. 

How can I get the Arduino IDE to use my new start up code?
The Arduino builder is case sensitive and will only see files that end in .S and not files that end in .s.

Renaming the new start up file to startup.S and then deleting the precomplied core archive fixed the problem.

Note that committing this change to git slightly complicated!