rtcds 'make' fails with uppercase filenames

Steps to reproduce (case sensitive):

1. Execute rtcds make x2iopee2_dac18AO8_test

   make fails (see log build_fail.log)

fatal error: x2iopee2_dac18ao8_test.h: No such file or directory

2. Save x2iopee2_dac18AO8_test.mdl as x2iopee2_dac18ao8_test.mdl in simulink

3. Execute rtcds make x2iopee2_dac18ao8_test

   make succeeds (see log build_good.log)

The issue appears to be with the string passed to GCC for FE_HEADER. The string is given in all lower case letters, but the header file retains the original model file name case. The header file x2iopee2_dac18AO8_test.h does exist on the system.

x2iopee2_dac18ao8_test.mdl x2iopee2_dac18AO8_test.mdl