[PATCH] prevent -Wno-system-headers from suppressing -Wstringop-overflow (PR 79214)

[Andreas Schwab]

I see this failure on aarch64 with -mabi=ilp32:

FAIL: gfortran.dg/alloc_comp_auto_array_2.f90   -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions  (test for excess errors)
Excess errors:
/opt/gcc/gcc-20170505/gcc/testsuite/gfortran.dg/alloc_comp_auto_array_2.f90:33:0: Warning: '__builtin_memcpy': specified size between 2147483648 and 4294967295 exceeds maximum object size 2147483647 [-Wstringop-overflow=]

Andreas.

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Andreas Schwab, schwab@linux-m68k.org
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