lineage: kernel: Use getconf instead of nproc

# Clear this first to prevent accidental poisoning from env

KERNEL_MAKE_FLAGS :=

# Add back threads, ninja cuts this to $(nproc)/2

KERNEL_MAKE_FLAGS += -j$(shell prebuilts/tools-lineage/$(HOST_PREBUILT_TAG)/bin/nproc --all)

# Add back threads, ninja cuts this to $(getconf _NPROCESSORS_ONLN)/2

KERNEL_MAKE_FLAGS += -j$(shell getconf _NPROCESSORS_ONLN)

ifeq ($(TARGET_KERNEL_CLANG_COMPILE),false)

  ifeq ($(KERNEL_ARCH),arm)