Convert $(sort) to Starlark

This is mostly so that we can not error out when
seeing sort inside a `include $(sort $(wildcard foo/*.mk))`.

Bug: 218736658
Test: go test
Change-Id: I827ecfc751a908227cb2dd9ed1e4b3f313791a16
diff --git a/mk2rbc/mk2rbc.go b/mk2rbc/mk2rbc.go
index 8807437..5ce031d 100644
--- a/mk2rbc/mk2rbc.go
+++ b/mk2rbc/mk2rbc.go
@@ -110,6 +110,7 @@
 	"require-artifacts-in-path-relaxed":    &simpleCallParser{name: baseName + ".require_artifacts_in_path_relaxed", returnType: starlarkTypeVoid},
 	// TODO(asmundak): remove it once all calls are removed from configuration makefiles. see b/183161002
 	"shell":    &shellCallParser{},
+	"sort":     &simpleCallParser{name: baseName + ".mksort", returnType: starlarkTypeList},
 	"strip":    &simpleCallParser{name: baseName + ".mkstrip", returnType: starlarkTypeString},
 	"subst":    &substCallParser{fname: "subst"},
 	"warning":  &makeControlFuncParser{name: baseName + ".mkwarning"},
diff --git a/mk2rbc/mk2rbc_test.go b/mk2rbc/mk2rbc_test.go
index 3698813..f94aa18 100644
--- a/mk2rbc/mk2rbc_test.go
+++ b/mk2rbc/mk2rbc_test.go
@@ -1022,12 +1022,13 @@
 `,
 	},
 	{
-		desc:   "strip function",
+		desc:   "strip/sort functions",
 		mkname: "product.mk",
 		in: `
 ifeq ($(filter hwaddress,$(PRODUCT_PACKAGES)),)
    PRODUCT_PACKAGES := $(strip $(PRODUCT_PACKAGES) hwaddress)
 endif
+MY_VAR := $(sort b a c)
 `,
 		expected: `load("//build/make/core:product_config.rbc", "rblf")
 
@@ -1036,6 +1037,7 @@
   if "hwaddress" not in cfg.get("PRODUCT_PACKAGES", []):
     rblf.setdefault(handle, "PRODUCT_PACKAGES")
     cfg["PRODUCT_PACKAGES"] = (rblf.mkstrip("%s hwaddress" % " ".join(cfg.get("PRODUCT_PACKAGES", [])))).split()
+  g["MY_VAR"] = rblf.mksort("b a c")
 `,
 	},
 	{