libm: fix compile error
libm: fix compile error

Fix a compile error when __UCLIBC_SUSV3_LEGACY__ is disabled.

Reported-by: Paolo Mantegazza <ef7e2758793540e586cdbf5f56260144dd969b69@polimi.it>

kraj/uclibc-ng,wbx-github/uclibc-ng,wbx-github/uclibc-ng,kraj/uclibc-ng,wbx-github/uclibc-ng,wbx-github/uclibc-ng,kraj/uclibc-ng,kraj/uclibc-ng