Couldn't compile c files in MATLAB_R2012b and OS X 10.12.6 El Capitan

Hi everyone,

I try to compile c files in MATLAB_R2012b, but I couldn't. It releases an error when I try mex hello.c for example. The error likes:

Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
In file included from hello.c:1:
In file included from /Applications/MATLAB_R2012b.app/extern/include/mex.h:58:
In file included from /Applications/MATLAB_R2012b.app/extern/include/matrix.h:294:
/Applications/MATLAB_R2012b.app/extern/include/tmwtypes.h:819:9: error: unknown type name 'char16_t'
typedef char16_t CHAR16_T;
        ^
1 error generated.

      mex: compile of ' "hello.c"' failed.

Error using mex (line 206)
Unable to complete successfully.

I try to get gcc version, it is

gcc (GCC) 5.3.0
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

I try which gcc, it is

/usr/local/bin/gcc

Meanwhile, I try whereis gcc, it is

/usr/bin/gcc

I attach the mexopts.sh file below. Could anyone let me know how to fix that problem. Thank you very much!