introduce _NBL_JOBS_AMOUNT_ and increase speed of DXC builds (TODO for future: use it anywhere we have custom commands we can specify jobs amount with)

Author: AnastaZIuk

src/nbl/CMakeLists.txt

@@ -3,6 +3,8 @@
 # This file is part of the "Nabla Engine".
 # For conditions of distribution and use, see copyright notice in nabla.h
 
+include(ProcessorCount)
+
 #[[
 macro(FindLibraryAndSONAME _LIB)
   string(TOUPPER ${_LIB} _UPPERLNAME)
@@ -546,8 +548,15 @@ if(_NBL_ENABLE_DXC_COMPILE_TESTS_)
 	add_dependencies(Nabla HLSL_NABLA_COMPILE_TEST)
 endif()
 
+if(NOT DEFINED _NBL_JOBS_AMOUNT_)
+	ProcessorCount(_NBL_JOBS_AMOUNT_)
+	if(_NBL_JOBS_AMOUNT_ EQUAL 0)
+		set(_NBL_JOBS_AMOUNT_ 1)
+	endif()
+endif()
+
 add_custom_command(OUTPUT "${DXC_LIB}" "${DXC_DLL}"
-	COMMAND "${CMAKE_COMMAND}" --build "${DXC_BUILD_DIR}" --target dxcompiler --config $<IF:$<CONFIG:Debug>,Debug,Release> -v --clean-first
+	COMMAND "${CMAKE_COMMAND}" --build "${DXC_BUILD_DIR}" --target dxcompiler --config $<IF:$<CONFIG:Debug>,Debug,Release> -v -j${_NBL_JOBS_AMOUNT_} --clean-first
 	VERBATIM
 	COMMAND_EXPAND_LISTS
 )