crypto: move crypto objects out of libqemuutil.la

Future patches will be adding more crypto related APIs which
rely on QOM infrastructure. This creates a problem, because
QOM relies on library constructors to register objects. When
you have a file in a static .a library though which is only
referenced by a constructor the linker is dumb and will drop
that file when linking to the final executable :-( The only
workaround for this is to link the .a library to the executable
using the -Wl,--whole-archive flag, but this creates its own
set of problems because QEMU is relying on lazy linking for
libqemuutil.a. Using --whole-archive majorly increases the
size of final executables as they now contain a bunch of
object code they don't actually use.

The least bad option is to thus not include the crypto objects
in libqemuutil.la, and instead define a crypto-obj-y variable
that is referenced directly by all the executables that need
this code (tools + softmmu, but not qemu-ga). We avoid pulling
entire of crypto-obj-y into the userspace emulators as that
would force them to link to gnutls too, which is not required.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

Makefile.objs

@@ -2,7 +2,6 @@
 # Common libraries for tools and emulators
 stub-obj-y = stubs/
 util-obj-y = util/ qobject/ qapi/ qapi-types.o qapi-visit.o qapi-event.o
-util-obj-y += crypto/
 
 #######################################################################
 # block-obj-y is code used by both qemu system emulation and qemu-img
@@ -21,6 +20,11 @@ block-obj-y += coroutine-$(CONFIG_COROUTINE_BACKEND).o
 
 block-obj-m = block/
 
+#######################################################################
+# crypto-obj-y is code used by both qemu system emulation and qemu-img
+
+crypto-obj-y = crypto/
+crypto-aes-obj-y = crypto/
 
 ######################################################################
 # smartcard