Build lighting for single stationally light level generates a shadow map in PF_B8G8R8A8 format

void FShadowMapPendingTexture::StartEncoding(ULevel* LightingScenario, ITextureCompressorModule* Compressor)
{
...
 
		// Create the uncompressed top mip-level.
		TArray< TArray<FFourDistanceFieldSamples> > MipData;
		const int32 NumChannelsUsed = FShadowMap2D::EncodeSingleTexture(LightingScenario, *this, Texture, MipData);
 
		Texture->Source.Init2DWithMipChain(GetSizeX(), GetSizeY(), NumChannelsUsed == 1 ? TSF_G8 : TSF_BGRA8);
		Texture->CompressionSettings = NumChannelsUsed == 1 ? TC_Grayscale : TC_Default; //work around
		Texture->MipGenSettings = TMGS_LeaveExistingMips;
		Texture->CompressionNone = true;