Add support for multiprocessing for the tests.

Makefile

@@ -4,6 +4,12 @@ SHELL := bash
 .DELETE_ON_ERROR:
 MAKEFLAGS += --warn-undefined-variables
 MAKEFLAGS += --no-builtin-rules
+TESTJOBS := 4
+OS:=$(shell uname -s)
+
+ifeq ($(OS),Linux)
+  TESTJOBS:=$(shell nproc)
+endif
 
 ifeq ($(origin .RECIPEPREFIX), undefined)
   $(error This Make does not support .RECIPEPREFIX. Please use GNU Make 4.0 or later)
@@ -24,15 +30,15 @@ clean:
 
 .PHONY: test
 test:
-> cargo test --lib --test test_loader
+> cargo test --lib --test test_loader -- --test-threads $(TESTJOBS)
 
 .PHONY: integrationtest
 integrationtest:
-> cargo test --no-fail-fast --test test_loader
+> cargo test --no-fail-fast --test test_loader -- --test-threads $(TESTJOBS)
 
 .PHONY: unittest
 unittest:
-> cargo test --lib
+> cargo test --lib -- --test-threads $(TESTJOBS)
 
 .PHONY: run
 run: