Support turning phony warnings into errors

These still default to warnings, but if a board decides to set
BOARD_BROKEN_PHONY_TARGETS := false, they'll turn into errors. More
likely I'll just be marking the broken targets as broken, then switching
the logic here to be like the dup rules warnings/errors.

Test: On a build with warnings, try <missing>, "false", and "true"
Change-Id: I041e1ff4618c4114ec43015b6c0ae1b49b36b6f8

ui/build/dumpvars.go

@@ -165,10 +165,12 @@ func runMakeProductConfig(ctx Context, config Config) {
 		// Whether --werror_overriding_commands will work
 		"BUILD_BROKEN_DUP_RULES",
 
+		// Used to turn on --werror_ options in Kati
+		"BUILD_BROKEN_PHONY_TARGETS",
+
 		// Not used, but useful to be in the soong.log
 		"BUILD_BROKEN_ANDROIDMK_EXPORTS",
 		"BUILD_BROKEN_DUP_COPY_HEADERS",
-		"BUILD_BROKEN_PHONY_TARGETS",
 	}, exportEnvVars...), BannerVars...)
 
 	make_vars, err := dumpMakeVars(ctx, config, config.Arguments(), allVars, true)
@@ -196,4 +198,5 @@ func runMakeProductConfig(ctx Context, config Config) {
 
 	config.SetPdkBuild(make_vars["TARGET_BUILD_PDK"] == "true")
 	config.SetBuildBrokenDupRules(make_vars["BUILD_BROKEN_DUP_RULES"] == "true")
+	config.SetBuildBrokenPhonyTargets(make_vars["BUILD_BROKEN_PHONY_TARGETS"] != "false")
 }