Revert "Add peak RSS stats to GC perf dump"

This reverts commit b4dad1bc.

Reason for revert: mincore() is a linux-specific syscall. Failing builds on non-linux targets.

Test: art/test/testrunner/testrunner.py --target
--runtime-option=-XX:DumpGCPerformanceOnShutdown should not print RSS
info.
Change-Id: I7b39e40a1096ca1bfbfd61c9430beaaeeee65903