/usr/include/openlibm/ is in libopenlibm-dev 0.5.4+dfsg-3.
This file is owned by root:root, with mode 0o755.
..
/usr/include/openlibm/aarch64_fpmath.h
/usr/include/openlibm/amd64_fpmath.h
/usr/include/openlibm/bsd_cdefs.h
/usr/include/openlibm/cdefs-compat.h
/usr/include/openlibm/fpmath.h
/usr/include/openlibm/i386_fpmath.h
/usr/include/openlibm/k_log.h
/usr/include/openlibm/k_logf.h
/usr/include/openlibm/math_private.h
/usr/include/openlibm/math_private_openbsd.h
/usr/include/openlibm/mips_fpmath.h
/usr/include/openlibm/openlibm.h
/usr/include/openlibm/openlibm_complex.h
/usr/include/openlibm/openlibm_fenv.h
/usr/include/openlibm/openlibm_fenv_amd64.h
/usr/include/openlibm/openlibm_fenv_arm.h
/usr/include/openlibm/openlibm_fenv_i387.h
/usr/include/openlibm/openlibm_fenv_mips.h
/usr/include/openlibm/openlibm_fenv_powerpc.h
/usr/include/openlibm/openlibm_math.h
/usr/include/openlibm/powerpc_fpmath.h
/usr/include/openlibm/types-compat.h