Fails to compile under Linux (Arch)

[Fuyukai]

ecsparse.y: In function ‘yyparse’:
ecsparse.y:1148:32: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
ecsparse.y:1149:32: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
ecsparse.y:1150:32: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
ecsparse.y:1151:32: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
ecsparse.y: In function ‘expression_operation_new’:
ecsparse.y:2274:33: warning: passing argument 1 of ‘expression_optimize’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
ecsparse.y:106:49: note: expected ‘parser_state_t *’ {aka ‘struct <anonymous> *’} but argument is of type ‘const parser_state_t *’ {aka ‘const struct <anonymous> *’}
ecsparse.y: At top level:
ecsparse.y:2813:1: error: conflicting types for ‘labels_adjust’
ecsparse.y:160:13: note: previous declaration of ‘labels_adjust’ was here
ecsparse.y:160:13: warning: ‘labels_adjust’ used but never defined
make[2]: *** [thecl/CMakeFiles/thecl.dir/build.make:94: thecl/CMakeFiles/thecl.dir/ecsparse.c.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:422: thecl/CMakeFiles/thecl.dir/all] Error 2
make: *** [Makefile:150: all] Error 2

Versions:

$ pacman -Q bison flex cmake gcc
bison 3.5.4-1
flex 2.6.4-3
cmake 3.17.2-1
gcc 9.3.0-1