sst++ does not pass flags correctly

[burlen]

sst++ in a standalone build of v13.1.0_Final of does not pass flags such as -DFOO through.

to reproduce:

test.cc

#if defined(FOO)
foo // this should error out
#else
int foo(int f) { return f + 1; };
#endif

This code should not compile if -DFOO is passed to the compiler. for example using g++

 g++ test.cc -c  -DFOO
test.cc:2:1: error: 'foo' does not name a type
    2 | foo // this should error out
      | ^~~

This is the expected and correct result. However, with sst++ the define is not propagated

sst++ test.cc -c  -DFOO

a .o file is produced, but this command should fail to compile.