Make host valgrind work with clang/llvm.

Bug: 28454823
* Add -fno-builtin-memset flag.

Bug: 31035712
* Make esp 16-byte aligned before calling x86 functions.
Bug: https://bugs.kde.org/show_bug.cgi?id=368120

Note that this does not fix other errors on x86 emulator.

Change-Id: Ibc19d0902aaba68edbb9f3758da368c35294128b
Test: Run valgrind on linux host and arm/x86 targets.
Test: In art run "mm valgrind-test-art-host"
4 files changed