"libmklccgdll" appears to be a common misspelling or a specific concatenation of libmkl_ccg.dll , a Dynamic Link Library (DLL) component of the Intel® oneAPI Math Kernel Library (oneMKL) This specific DLL is typically associated with Conditioned Conjugate Gradient (CCG)
The library, libmklccgdll , was supposed to handle the Conjugate Gradient solver. The standard practice was to let the runtime choose the interface. But Elias was desperate. He was telling the linker to ignore the legacy interface and instantiate a fresh memory profile for the solver. libmklccgdll new
set MKL_THREADING_LAYER=GNU # or INTEL