python3-numpy: Always use libgcc for unwinder on aarch64

python3-numpy: Always use libgcc for unwinder on aarch64

With libgcc (working):

Result: inf
Warnings: ['overflow encountered in cast']

With compiler-rt (failing):

Result: inf (probably still correct)
Warnings: [] (no warnings generated)

The issue is likely that compiler-rt on AArch64 doesn't trigger
the floating-point exceptions that NumPy expects for overflow
detection in type casting operations.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>