change stride to 4 instead of 1 if int8 is not supported

[Rekt3421]

please see issue #1396 for more details

[Rekt3421]

Is a unit test needed for this? Seems a little trivial @rjodinchr ?

[rjodinchr]

This is not the only place where we create spv::DecorationArrayStride.
I would like to have every place fixed.

Also, why 2? when int8 is not supported, it is converted to int32 not int16.

We would definitely need tests here. At least the one from the issue.

[rjodinchr]

This one feels like a good one as well:

// RUN: clspv -int8=0 %target %s -o %t.spv
// RUN: spirv-dis -o %t2.spvasm %t.spv
// RUN: FileCheck %s < %t2.spvasm
// RUN: spirv-val --target-env vulkan1.0 %t.spv

constant uchar b[4] = {[0]=42, [1]=13, [2]=0, [3]=5};

void kernel __attribute__((reqd_work_group_size(4, 1, 1))) foo(global uchar* a)
{
  *a = b[get_local_id(0)];
}

// CHECK-DAG:  [[uint:%[^ ]+]] = OpTypeInt 32 0
// CHECK-DAG:  OpTypePointer StorageBuffer [[struct:%[^ ]+]]
// CHECK-DAG:  [[struct]] = OpTypeStruct [[runtimearr:%[^ ]+]]
// CHECK-DAG:  OpDecorate [[runtimearr]] ArrayStride 4

You will note that even if you change ArrayStride 4 to ArrayStride 2 in the test, it is still not passing with 2. It would be failing with the following message:

Structure id 15 decorated as Block for variable in StorageBuffer storage class must follow standard storage buffer layout rules: member 0 contains an array with stride 2 not satisfying alignment to 4

[Rekt3421]

Will add the test from the issue as well.

[rjodinchr]

Please avoid code duplication. Make a function for it.