build: fix host dex2oat runtime args

The dalvik.vm.* properties are in PRODUCT_DEFAULT_PROPERTY_OVERRIDES,
not PRODUCT_PROPERTY_OVERRIDES.
Use $(call func,args) for user defined functions
Prepend the property contents with -Xms or -Xmx when passing to
dex2oat.  This only worked before because DEX2OAT_XMS, etc. were blank
due to the first two  bugs, which resulted in --runtime-arg --runtime-arg
and anything starting with -- as the argument to --runtime-arg is
silently ignored.

Change-Id: Ifa30038b397355171fefcc5248eea033bb634036