Add support for gzipping html output.

Bug: 68860345
Bug: 151177513
Bug: 151953481
Bug: 213388645
Bug: 210912771

Test: m all
Test: m systemlicense
Test: m htmlnotice; out/soong/host/linux-x85/htmlnotice ...

where ... is -o=html.gz followed by the path to the .meta_lic file for
the system image. In my case if

$ export PRODUCT=$(realpath $ANDROID_PRODUCT_OUT --relative-to=$PWD)

the rest of ... can be expressed as:

${PRODUCT}/gen/META/lic_intermediates/${PRODUCT}/system.img.meta_lic

Change-Id: I7a42d5186876609a401956754e3dcff64211fb15