This prevents the compiler from optimizing calloc into an
infinite recursive call.
For example a call to malloc + memset zero at GCC -O2 will be
replaced by a call to calloc. This causes infinite recursion
if the function being implemented *is* calloc.
fno-builtin-malloc forces the compiler to avoid this optimization.
Signed-off-by: Grant Ramsay <gramsay@enphaseenergy.com>
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