c: After issuing errors about array size, for error-recovery don't make the array...

c: After issuing errors about array size, for error-recovery don't make the array VLA [PR93573]

After we report various errors about array size, we set for error-recovery
the size to be 1, but because size_int_const is false, it still means we
pretend the array is a VLA, can emit a second diagnostics in that case etc.
E.g.
$ ./cc1.unpatched -quiet a.c
a.c:1:5: error: size of array ‘f’ has non-integer type
    1 | int f[100.0];
      |     ^
a.c:1:1: warning: variably modified ‘f’ at file scope
    1 | int f[100.0];
      | ^~~
$ ./cc1 -quiet a.c
a.c:1:5: error: size of array ‘f’ has non-integer type
    1 | int f[100.0];
      |     ^

2020-03-28  Jakub Jelinek  <jakub@redhat.com>

	PR c/93573
	* c-decl.c (grokdeclarator): After issuing errors, set size_int_const
	to true after setting size to integer_one_node.

	* gcc.dg/pr93573-1.c: New test.
	* gcc.dg/pr93573-2.c: New test.