[OpenMP] Add "not" to test dependencies.

The `not` program is used to test executions prefixed with `%libomptarget-run-fail-`. Currently `not` is not used for libomp tests, but might be used in the future and its dependency does not add any additional burden over the already established `FileCheck` dependency.

Required to add libomptarget testing to the Phabricator pre-merge check (see google/llvm-premerge-checks#368)

Reviewed By: jdenny, JonChesterfield

Differential Revision: https://reviews.llvm.org/D115454

Author: Meinersbur

openmp/cmake/OpenMPTesting.cmake

@@ -196,14 +196,14 @@ function(add_openmp_testsuite target comment)
         ${comment}
         ${ARG_UNPARSED_ARGUMENTS}
         EXCLUDE_FROM_CHECK_ALL
-        DEPENDS clang FileCheck ${ARG_DEPENDS}
+        DEPENDS clang FileCheck not ${ARG_DEPENDS}
         ARGS ${ARG_ARGS}
       )
     else()
       add_lit_testsuite(${target}
         ${comment}
         ${ARG_UNPARSED_ARGUMENTS}
-        DEPENDS clang FileCheck ${ARG_DEPENDS}
+        DEPENDS clang FileCheck not ${ARG_DEPENDS}
         ARGS ${ARG_ARGS}
       )
     endif()