makefiles/info.inc.mk: provide info targets about toolchain support

makefiles/info.inc.mk

 .PHONY: info-objsize info-buildsizes info-build info-boards-supported \
         info-features-missing info-modules info-cpu \
         info-features-provided info-features-required \
-        info-debug-variable-%
+        info-debug-variable-% info-toolchains-supported \
+        check-toolchain-supported
 
 info-objsize:
 	@case "$(SORTROW)" in \
@@ -130,3 +131,9 @@ info-features-missing:
 
 info-debug-variable-%:
 	@echo $($*)
+
+info-toolchains-supported:
+	@echo $(filter-out $(TOOLCHAINS_BLACKLIST),$(TOOLCHAINS_SUPPORTED))
+
+check-toolchain-supported:
+	@exit $(if $(filter $(TOOLCHAIN),$(filter-out $(TOOLCHAINS_BLACKLIST),$(TOOLCHAINS_SUPPORTED))),0,1)