spirv: Ignore WorkgroupSize in non-compute stages

If a SPIR-V module contains for example both a geometry and a compute shader, when processing the geometry shader its vertices out, input primitive and output primitive attributes would get overwritten by the value of the WorkgroupSize.

; SPIR-V
; Version: 1.5
; Generator: Khronos; 17
; Bound: 12
; Schema: 0
               OpCapability Geometry
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Geometry %main "main"
               OpEntryPoint GLCompute %main_0 "main"
               OpExecutionMode %main InputPoints
               OpExecutionMode %main Invocations 1
               OpExecutionMode %main OutputTriangleStrip
               OpExecutionMode %main OutputVertices 4
               OpExecutionMode %main_0 LocalSize 1 1 1
               OpSource GLSL 460
               OpSource GLSL 460
               OpName %main "main"
               OpName %main_0 "main"
               OpModuleProcessed "Linked by SPIR-V Tools Linker"
               OpDecorate %gl_WorkGroupSize BuiltIn WorkgroupSize
       %void = OpTypeVoid
          %6 = OpTypeFunction %void
       %uint = OpTypeInt 32 0
     %v3uint = OpTypeVector %uint 3
     %uint_1 = OpConstant %uint 1
%gl_WorkGroupSize = OpConstantComposite %v3uint %uint_1 %uint_1 %uint_1
       %main = OpFunction %void None %6
         %10 = OpLabel
               OpReturn
               OpFunctionEnd
     %main_0 = OpFunction %void None %6
         %11 = OpLabel
               OpReturn
               OpFunctionEnd

Running spirv_to_nir on the SPIR-V sample above and for the geometry entry point would say that (among others):

• vertices out: 1
• input primitive: LINES
• output primitive: LINES

By removing any reference to %gl_WorkGroupSize, the output would change to (among others):

• vertices out: 4
• input primitive: POINTS
• output primitive: TRIANGLE_STRIP