meson: convert the speed tests

Use meson benchmark() for them, adjust mtest2make.py for that.
A new target "make bench" can be used to run all benchmarks.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20200828110734.1638685-14-marcandre.lureau@redhat.com>
[Rewrite mtest2make part. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/Makefile b/Makefile
index ed354c4..d4d6a67 100644
--- a/Makefile
+++ b/Makefile
@@ -64,7 +64,7 @@
 # reread (and MESON won't be empty anymore).
 ifneq ($(MESON),)
 Makefile.mtest: build.ninja scripts/mtest2make.py
-	$(MESON) introspect --tests | $(PYTHON) scripts/mtest2make.py > $@
+	$(MESON) introspect --tests --benchmarks | $(PYTHON) scripts/mtest2make.py > $@
 -include Makefile.mtest
 endif
 
@@ -283,6 +283,7 @@
 	@echo  ''
 	@echo  'Test targets:'
 	$(call print-help,check,Run all tests (check-help for details))
+	$(call print-help,bench,Run all benchmarks)
 	$(call print-help,docker,Help about targets running tests inside containers)
 	$(call print-help,vm-help,Help about targets running tests inside VM)
 	@echo  ''