diagnostics: ignore -fmax-errors for ICE

diagnostics: ignore -fmax-errors for ICE

Right now I see:
./xgcc -B. ~/Programming/testcases/json.i -c -O2 -fmax-errors=1
/home/marxin/Programming/testcases/json.i: In function ‘json_variant_type’:
/home/marxin/Programming/testcases/json.i:22:1: error: non-integral type switch statement
   22 | }
      | ^
int *
switch (v_2(D)) <default: <L16> [INV], case 0B: <L11> [INV], case 5B: <L12> [INV], case 6B: <L13> [INV], case 7B: <L14> [INV], case 8B: <L15> [INV]>
compilation terminated due to -fmax-errors=1.

with the patch I get:

./xgcc -B. ~/Programming/testcases/json.i -c -O2 -fmax-errors=1 -c
/home/marxin/Programming/testcases/json.i: In function ‘json_variant_type’:
/home/marxin/Programming/testcases/json.i:22:1: error: non-integral type switch statement
   22 | }
      | ^
int *
switch (v_2(D)) <default: <L16> [INV], case 0B: <L11> [INV], case 5B: <L12> [INV], case 6B: <L13> [INV], case 7B: <L14> [INV], case 8B: <L15> [INV]>
during GIMPLE pass: iftoswitch
/home/marxin/Programming/testcases/json.i:22:1: internal compiler error: verify_gimple failed
0xe4478c verify_gimple_in_cfg(function*, bool)
	/home/marxin/Programming/gcc/gcc/tree-cfg.c:5467
0xd201cf execute_function_todo
	/home/marxin/Programming/gcc/gcc/passes.c:2042
0xd2101c do_per_function
	/home/marxin/Programming/gcc/gcc/passes.c:1687
0xd2101c execute_todo
	/home/marxin/Programming/gcc/gcc/passes.c:2096
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

gcc/ChangeLog:

	* diagnostic.c (diagnostic_report_diagnostic): ICE causes to
	terminate compiler immediately, so I guess it should be printed
	always.