Include the amr encoder shared library in all builds.

Change-Id: Ib2c4b8ee73d0615e712c672b9badd156906811e6
diff --git a/target/product/core.mk b/target/product/core.mk
index 5791048..a8d2746 100644
--- a/target/product/core.mk
+++ b/target/product/core.mk
@@ -88,6 +88,7 @@
     libstagefright_soft_aacdec \
     libstagefright_soft_aacenc \
     libstagefright_soft_amrdec \
+    libstagefright_soft_amrnbenc \
     libstagefright_soft_g711dec \
     libstagefright_soft_h264dec \
     libstagefright_soft_mp3dec \