Build/compile errors because of compilerOptions in legacy_code - matlab

Question

I want to create some trivial S-function with legacy_code for my MexTest.c:
legacy_code('compile', specs, compilerOptions)
There are 2 macros (TEST_DEF1 and TEST_DEF2), which I want to put into compilerOptions. The 2 macros are used in the function TestFnc().
But somehow, the TestFnc() does not see the 2 macros defined in compilerOptions before...
MexTest.c:
#include "MexTest.h"
void TestFnc(double *p_u, double *p_y)
{
*p_y = *p_u + 1;
#ifndef TEST_DEF1
#error "undefined: TEST_DEF1"
#endif
#ifndef TEST_DEF2
#error "undefined: TEST_DEF2"
#endif
}
MexTest.h:
#ifndef MEXTEST_H_
#define MEXTEST_H_
void TestFnc(double *p_u, double *p_y);
#endif
legacy_code tool
specs = legacy_code('initialize');
specs.HeaderFiles = {'MexTest.h'};
specs.SourceFiles = {'MexTest.c'};
specs.SFunctionName = 'Test_SFunc_gen';
specs.OutputFcnSpec = 'void TestFnc(double u1[1], double y1[1])';
%% Compile C-MEX-s-function
legacy_code('sfcn_cmex_generate', specs);
legacy_code('generate_for_sim',specs);
legacy_code('compile', specs, {'-DTEST_DEF1', '-DTEST_DEF2'});
Mex Build Errors:
### Start Compiling Test_SFunc_gen
mex('-IC:\Users\xxxx\Documents\', '-c', '-outdir', 'C:\Users\xxxx\AppData\Local\Temp\tp05e00c12_2732_4dab_a0f8_f30bd05992f8', 'C:\Users\xxxx\Documents\MexTest.c')
Building with 'MinGW64 Compiler (C)'.
Error using mex
C:\Users\xxxx\Documents\MexTest.c: In function 'TestFnc':
C:\Users\xxxx\Documents\MexTest.c:8:10: error: #error "undefined: TEST_DEF1"
#error "undefined: TEST_DEF1"
C:\Users\xxxx\Documents\MexTest.c:12:10: error: #error "undefined: TEST_DEF2"
#error "undefined: TEST_DEF2"
How could I use the -D option correctly for my case?
(Matlab version 2021a)