Vendor lib can use rsDispatch.h

In order to allow vendor libs to use rsDispatch.h, jni releated part of
the header is guarded with RS_COMPATIBILITY_LIB since jni.h is not
available to vendors.

Exempt-From-Owner-Approval: Only current owner is this a mailing list
[email protected]
And mailing lists aren't currently supported.

Bug: 37342627
Test: BOARD_VNDK_VERSION=current m -j
[email protected]
Test: m -j librsjni

Merged-In: I980593db946207a97a69abc8397beb18105e6ed2
Change-Id: I980593db946207a97a69abc8397beb18105e6ed2
(cherry picked from commit bac72f8b9d90ea0c5bdc0b05e02d418ebc83db25)
diff --git a/cpp/Android.bp b/cpp/Android.bp
index 710c690..c3b44ed 100644
--- a/cpp/Android.bp
+++ b/cpp/Android.bp
@@ -10,6 +10,7 @@
         "-Werror",
         "-Wno-unused-parameter",
         "-std=c++11",
+        "-DRS_COMPATIBILITY_LIB",
     ],
 
     sdk_version: "9",