Fix up a few bionic tests for the clang-r339409 update.

Disable -Wmemset-transposed-args to ensure that FORTIFY still works
without it. Also, we can finally enable checking for
FLT_HAS_SUBNORM/DBL_HAS_SUBNORM/LDBL_HAS_SUBNORM now that those are
available in Clang.

Bug: http://b/110779387
Test: build and run bionic unit tests
Change-Id: I4bf19b870c44d981ecbd1089d0ae6a2496be5441