Turn off ipa-ra in builtins test (PR91059)

Turn off ipa-ra in builtins test (PR91059)

The gcc.c-torture/execute/builtins/lib directory contains a reimplementation
of many C library string functions, which causes non-trivial register allocation
bugs with LTO and static linked libraries.  To fix this long-standing test issue,
turn off ipa-ra which avoids the register corruption across calls.  All builtin
torture tests now pass on aarch64-none-elf.  Committed as obvious.
See PR78529 for more details.

    testsuite/
	PR testsuite/78529
	* gcc.c-torture/execute/builtins/builtins.exp: Add -fno-ipa-ra.

From-SVN: r273452