Add cache dir to context object.

Change-Id: Icc3220329fbaee7d453259fbe1cbf34d145d195c
diff --git a/rsContext.cpp b/rsContext.cpp
index 9a86c86..f8088b0 100644
--- a/rsContext.cpp
+++ b/rsContext.cpp
@@ -763,6 +763,10 @@
 #endif
 }
 
+void rsi_ContextSetCacheDir(Context *rsc, const char *cacheDir, size_t cacheDir_length) {
+    rsc->setCacheDir(cacheDir, cacheDir_length);
+}
+
 void rsi_ContextBindSampler(Context *rsc, uint32_t slot, RsSampler vs) {
     Sampler *s = static_cast<Sampler *>(vs);
 
@@ -940,4 +944,3 @@
     ObjectBase *ob = static_cast<ObjectBase *>(obj);
     (*name) = ob->getName();
 }
-