Don't build x86 valgrind.

valgrind's "supported platforms" page says:

  x86/Linux: up to and including SSSE3, but not higher -- no SSE4, AVX, AVX2.
  This target is in maintenance mode now..

  AMD64/Linux: up to and including AVX2. This is the primary development
  target and tends to be well supported.

A sentiment reiterated in the release notes for the current version:

    Whilst 3.12.0 continues to support the 32-bit x86 instruction set, we
    would prefer users to migrate to 64-bit x86 (a.k.a amd64 or x86_64)
    where possible.  Valgrind's support for 32-bit x86 has stagnated in
    recent years and has fallen far behind that for 64-bit x86
    instructions.  By contrast 64-bit x86 is well supported, up to and
    including AVX2.

Since our default build flags use SSE4 for x86, valgrind is not currently
usable.

Bug: http://b/38034461
Test: N/A
Change-Id: I97e5244d79c95c613ac43b98e6ee35d445c1b9f5
1 file changed