Expose spirv.core.grammar.json for libspirit

libspirit in frameworks/rs/rsov/compiler/spirit uses this json file to
generate a number of headers. Expose it explicitly instead of hardcoding
a path into the NDK prebuilts.

Test: m libspirit
Change-Id: Ibf81258997e73797ef258e1f2a7915e633a22383
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..fe1b80e
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,4 @@
+filegroup {
+    name: "spirv.core.grammar.json-1.1",
+    srcs: ["include/spirv/1.1/spirv.core.grammar.json"],
+}