unit: TOPT make arg to pass test options through to the test binary

Sponsored-by: TrueNAS
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@truenas.com>
Closes #18586

tests/unit/Makefile.am

@@ -44,11 +44,11 @@ nodist_%C%_test_zap_SOURCES = \
 PHONY += unit unit-coverage
 
 _unit_run_%: %D%/%
-	@echo "  UNITTEST $<" ; $<
+	@echo "  UNITTEST $<" ; $< $(TOPT)
 
 _unit_coverage_%: %D%/%
 	@${LCOV} --quiet --zerocounters --directory $(top_srcdir) >/dev/null
-	@echo "  UNITTEST $<" ; $<
+	@echo "  UNITTEST $<" ; $< $(TOPT)
 	@${LCOV} --quiet --capture  \
 		--test-name $(subst _unit_coverage_, , $@) \
 		--directory $(top_srcdir) \

tests/unit/README.md

@@ -45,6 +45,10 @@ Running test suite with seed 0x18e131ac...
 ...
 ```
 
+The test framework provides various options for controlling how the tests are
+run. Add the `--help` switch for more info. If using the make rule, options can
+be passed via the `TOPT=` param.
+
 ### Building just for tests
 
 Recommended “minimum” build for just the unit tests, with additional debug to