message: Add optional debug dumping of postvs SPIR-V
diff: #include <float.h>
  #include <math.h>
  #include <algorithm>
  +#include "core/settings.h"
  #include "driver/shaders/spirv/spirv_editor.h"
  #include "driver/shaders/spirv/spirv_op_helpers.h"
  #include "vk_core.h"
  #include "vk_replay.h"
  #include "vk_shader_cache.h"
  +RDOC_DEBUG_CONFIG(rdcstr, Vulkan_Debug_PostVSDumpDirPath, "",
  + "Path to dump gnerated SPIR-V compute shaders for fetching post-vs.");
  +
  #undef None
  struct VkXfbQueryResult
  @@ -1984,10 +1988,16 @@ void VulkanReplay::FetchVSOut(uint32_t eventId, VulkanRenderState &state)
  m_pDriver->vkUpdateDescriptorSets(dev, numWrites, descWrites, 0, NULL);
  }
  + if(!Vulkan_Debug_PostVSDumpDirPath().empty())
  + FileIO::WriteAll(Vulkan_Debug_PostVSDumpDirPath() + "/debug_postvs_vert.spv", modSpirv);
  +
  ConvertToMeshOutputCompute(*refl, *pipeInfo.shaders[0].patchData,
  pipeInfo.shaders[0].entryPoint.c_str(), attrInstDivisor, drawcall,
  numVerts, numViews, modSpirv, bufStride);
  + if(!Vulkan_Debug_PostVSDumpDirPath().empty())
  + FileIO::WriteAll(Vulkan_Debug_PostVSDumpDirPath() + "/debug_postvs_comp.spv", modSpirv);
  +
  VkComputePipelineCreateInfo compPipeInfo = {VK_STRUCTURE_TYPE_COMPUTE_PIPELINE_CREATE_INFO};
  // repoint pipeline layout
  