libhsakmt - Add make option to package thunk as RPM

Add an option to libhsakmt to allow the thunk to be packaged as an RPM.
The default will remain being built as-is, but this can now be packaged
as an RPM by using "make src rpm" . build_thunk.sh will be modified to
reflect this new option.

Change-Id: I38e03d10cfb5035bdf0a87635a784c47a709a5b6

Makefile

@@ -5,6 +5,9 @@ all: lnx64a
 deb:
 	$(MAKE) -C src deb
 
+rpm:
+	$(MAKE) -C src rpm
+
 lnx64a:
 	$(MAKE) -C src lnx64a