Validate failures in sanity way

It seems like some of the sanity checks fail when running the test suite. To reproduce, run the test suite using:

make EXTRA_HC_OPTS='-debug -rtsopts' WAY=sanity THREADS=12

Results:

Unexpected failures:
   rts/T2783.run                                        T2783 [bad exit code] (sanity)
   rts/flags/T12870e.run                                T12870e [bad stdout] (sanity)
   rts/flags/T12870f.run                                T12870f [bad stdout] (sanity)
   ../../libraries/base/tests/length001.run             length001 [bad exit code] (sanity)
   ../../libraries/ghc-heap/tests/heap_all.run          heap_all [bad exit code] (sanity)
   rts/T7919.run                                        T7919 [bad exit code] (sanity)
   ../../libraries/base/tests/memo001.run               memo001 [bad exit code] (sanity)
   ../../libraries/hpc/tests/raytrace/hpc_raytrace.run  hpc_raytrace [bad exit code] (sanity)

T2783:

T2783: internal error: ASSERTION FAILED: file rts/ThreadPaused.c, line 314

Stack trace:
test: Failed to get stack frames of current process: no matching address range: Success
                  0x4a3fbd    set_initial_registers (rts/Libdw.c:288.0)
            0x7f9d70fd7a18    dwfl_thread_getframes (/usr/lib/x86_64-linux-gnu/libdw-0.170.so)
            0x7f9d70fd7efc    dwfl_getthread_frames (/usr/lib/x86_64-linux-gnu/libdw-0.170.so)
                  0x4a3eb6    libdwGetBacktrace (rts/Libdw.c:257.0)
                  0x474de3    rtsFatalInternalErrorFn (rts/RtsMessages.c:171.0)
                  0x474ad0    barf (rts/RtsMessages.c:48.0)
                  0x474b02    errorBelch (rts/RtsMessages.c:67.0)
                  0x479273    threadPaused (rts/ThreadPaused.c:318.0)
                  0x48ccdb    stg_returnToSched (rts/StgStartup.cmm:117.1)
                  0x48f428    stg_enter_info (rts/HeapStackCheck.cmm:166.1)
                  0x45fd18    integerzmgmp_GHCziIntegerziType_minusInteger_info (/home/omer/haskell/test)

    (GHC version 8.4.2 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
zsh: abort (core dumped)  ./T2783 +RTS -DS

memo001:

memo001: internal error: ASSERTION FAILED: file rts/sm/GCAux.c, line 44

    (GHC version 8.5.20180612 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
zsh: abort (core dumped)  ./memo001 +RTS -DS -A10k

length001:

length001: Stack space overflow: current size 33624 bytes.
length001: Use `+RTS -Ksize -RTS' to increase it.

Note that the test is run with -K8m.

hpc_raytrace: gets killed because of timeout.