It is enabled through math-use-builtins-fma.h if glibc is built
for VPFv4 (__ARM_FEATURE_FMA predefined by GCC), or through IFUNC
(testing HWCAP_ARM_VFPv4) otherwise.
Checked on arm-linux-gnueabihf.
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Adhemerval Zanella