support system server jars install in system_ext

Bug: 245383870
Bug: 155630745
Test:m nothing
Test:-
1.Add a jar installed in the system_ext partition toSYSTEMSERVERJARS
(e.g.b/245383870 PRODUCT_SYSTEM_SERVER_JARS_EXTRA += system_ext:oem-services)
2.Build a ROM
3.See the odex and vdex files generated in $ANDROID_PRODUCT_OUT/system_ext/framework/oat/
4.Flash the ROM to a device
5.Check the maps information of the system_server , the newly added odex has the r-xp flags
6.Run `adb shell am restart;adb root;adb shell setprop dalvik.vm.extra-opts
-verbose:deopt,heap,jit,oat,image,dex,verifier;`
7.Check ClassLoaderContext classpath size matching information
8.Run `atest art_standalone_odrefresh_tests`
`atest art_standalone_dexpreopt_tests`
`atest CtsSdkExtensionsTestCases`

Change-Id: Ib1083ee130b5fef9c23d56523868fa1e29be879a
Signed-off-by: liulvping <liulvping@xiaomi.com>