Fix typo in java system modules makevars

This was preventing us from actually using system module dependencies
from Make.

Fixes: 135679136
Test: EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9=true m legacy-performance-test-hostdex
Change-Id: Ic51c30d09cf39e35f2fe5f534a23273f450d9138
diff --git a/java/system_modules.go b/java/system_modules.go
index f71f452..c616249 100644
--- a/java/system_modules.go
+++ b/java/system_modules.go
@@ -138,7 +138,7 @@
 			fmt.Fprintln(w, makevar, ":=$=", strings.Join(system.properties.Libs, " "))
 			fmt.Fprintln(w)
 
-			makevar = "SOONG_SYSTEM_MODULE_DEPS_" + name
+			makevar = "SOONG_SYSTEM_MODULES_DEPS_" + name
 			fmt.Fprintln(w, makevar, ":=$=", strings.Join(system.outputDeps.Strings(), " "))
 			fmt.Fprintln(w)