[lit] Protect full test suite from FILECHECK_OPTS

[lit] Protect full test suite from FILECHECK_OPTS

lit's test suite calls lit multiple times for various sample test
suites.  `FILECHECK_OPTS` is safe for FileCheck calls in lit's test
suite.  It's not safe for FileCheck calls in the sample test suites,
whose output affects the results of lit's test suite.

Without this patch, only one such sample test suite is protected from
`FILECHECK_OPTS`, and I admit I haven't discovered other cases for
which I can produce false failures using `FILECHECK_OPTS`.  However,
it's hard to predict the future, especially false passes.  Thus, this
patch protects all existing and future sample test suites from
`FILECHECK_OPTS` (and the deprecated
`FILECHECK_DUMP_INPUT_ON_FAILURE`).

Reviewed By: probinson

Differential Revision: https://reviews.llvm.org/D65156

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@366980 91177308-0d34-0410-b5e6-96231b3b80d8