Only allow (int)trunc(x) to (int)x simplification with -ffp-int-builtin-inexact ...

Only allow (int)trunc(x) to (int)x simplification with -ffp-int-builtin-inexact [PR107723]

With -fno-fp-int-builtin-inexact, trunc is not allowed to raise
FE_INEXACT and it should produce an integral result (if the input is not
NaN or Inf).  Thus FE_INEXACT should not be raised.

But (int)x may raise FE_INEXACT when x is a non-integer, non-NaN, and
non-Inf value.  C23 recommends to do so in a footnote.

Thus we should not simplify (int)trunc(x) to (int)x if
-fno-fp-int-builtin-inexact is in-effect.

gcc/ChangeLog:

	PR middle-end/107723
	* convert.cc (convert_to_integer_1) [case BUILT_IN_TRUNC]: Break
	early if !flag_fp_int_builtin_inexact and flag_trapping_math.

gcc/testsuite/ChangeLog:

	PR middle-end/107723
	* gcc.dg/torture/builtin-fp-int-inexact-trunc.c: New test.