message: gltfpack: Update Basis SGD to track latest spec
  rc1 version of the specification removed globalFlags from global header,
  making existing files non-compliant.
diff: @@ -54,7 +54,6 @@ static const uint8_t Ktx2FileIdentifier[12] = {
  // KTX Specification: 3.12.2. Basis Universal Global Data
  struct Ktx2BasisGlobalHeader
  {
  - uint32_t globalFlags;
  uint16_t endpointCount;
  uint16_t selectorCount;
  uint32_t endpointsByteLength;
  @@ -259,7 +258,6 @@ std::string basisToKtx(const std::string& data, bool srgb, bool uastc)
  if (basis)
  {
  Ktx2BasisGlobalHeader sgd_header = {};
  - sgd_header.globalFlags = basis_header.m_flags;
  sgd_header.endpointCount = uint16_t(basis_header.m_total_endpoints);
  sgd_header.selectorCount = uint16_t(basis_header.m_total_selectors);
  sgd_header.endpointsByteLength = basis_header.m_endpoint_cb_file_size;
  