The `build_sources_library` is accidentlly being used when instead `build_sources_program` needs to be used.
build_sources_program fll/level_1/conversion.c fll/level_1/private-conversion.c fll/level_1/conversion/common.c
build_sources_program fll/level_1/directory.c fll/level_1/private-directory.c
-build_sources_library fll/level_1/path.c
+build_sources_program fll/level_1/path.c
build_sources_program fll/level_1/print.c fll/level_1/private-print.c fll/level_1/print/common.c
build_sources_program fll/level_2/error.c fll/level_2/private-error.c fll/level_2/error/common.c fll/level_2/error/string.c
build_sources_program fll/level_1/conversion.c fll/level_1/private-conversion.c fll/level_1/conversion/common.c
build_sources_program fll/level_1/directory.c fll/level_1/private-directory.c
-build_sources_library fll/level_1/path.c
+build_sources_program fll/level_1/path.c
build_sources_program fll/level_1/print.c fll/level_1/private-print.c fll/level_1/print/common.c
build_sources_program fll/level_2/error.c fll/level_2/private-error.c fll/level_2/error/common.c fll/level_2/error/string.c