Sort files in directories passed to jar

jar -C <dir> . produces a jar containing files in filesystem order,
which can vary between builds.  Manually find and sort the list of
files, and convert them into a list of -C <dir> <file> pairs.

Fixes: 64634025
Test: m -j checkbuild
Test: m -j out/target/product/sailfish/system/framework/ext.jar, check
      that entries are sorted
Test: m -j out/target/product/generic_arm64/system/framework/ext.jar on mac
Change-Id: I7dced6acbe621a60cd49daf17872941485602732