Sharing .o files

Greetings,

After cloning the required tag from chromium repo, we build a
clean version first. After the clean build is done, we patch the
sources with changes needed and we build a patched version. Clean
and patched versions are built in out/clean and out/patched
directories respectively.

Since number of patches are very low and touch a handful of CC
files, I tried copying contents of out/clean to out/patched
directory. As far as I could see copy went smoothly. However when
I try to build patched version, it does a full build and takes
same time as clean version build.

Is there any way to share .o files between two builds and just
build the delta like autoninja command does normally? Command I
normally execute is

autoninja -c out/clean chrome

or

autoninja -c out/patched chrome

Regards,

Niranjan