Fix -audio <name> and -no-audio processing.

Turns out that the string passed to putenv() must not be modified :-/

We provide our own win32 implementation for emulator-ui that doesn't
embed the os-win32.c QEMU-specific file.

Change-Id: I7260fbc37d23a5340dab589dfde577ef5eb10005
diff --git a/Makefile.android b/Makefile.android
index 735697c..3b1619b 100644
--- a/Makefile.android
+++ b/Makefile.android
@@ -242,6 +242,7 @@
     android/snapshot.c \
     android/main-common.c \
     android/main.c \
+    android/utils/setenv.c \
     vl-android-ui.c \
     android/protocol/core-connection.c \
     android/protocol/attach-ui-impl.c \