tests/test-fuzz-targets.t

tests: fix glob pattern for dynamic timer alignment

The number of space characters varies depending on the number of digits of the
timer, making some tests fail on slow machines in an unintended way:

```diff
--- /build/mercurial-6.1/tests/test-merge-halt.t
+++ /build/mercurial-6.1/tests/test-merge-halt.t.err
@@ -210,6 +210,6 @@
   merge halted after failed merge (see hg resolve)
   [240]
   $ hg shelve --list
-  default         (* ago)    changes to: foo (glob)
+  default         (11s ago)   changes to: foo
   $ hg unshelve --abort
   unshelve of 'default' aborted
ERROR: test-merge-halt.t output changed
```

Differential Revision: https://phab.mercurial-scm.org/D12381

#require test-repo py3

  $ cd $TESTDIR/../contrib/fuzz
  $ OUT=$TESTTMP ; export OUT

which(1) could exit nonzero, but that's fine because we'll still end
up without a valid executable, so we don't need to check $? here.

  $ if which gmake >/dev/null 2>&1; then
  >     MAKE=gmake
  > else
  >     MAKE=make
  > fi

  $ havefuzz() {
  >     cat > $TESTTMP/dummy.cc <<EOF
  > #include <stdlib.h>
  > #include <stdint.h>
  > int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) { return 0; }
  > int main(int argc, char **argv) {
  >     const char data[] = "asdf";
  >     return LLVMFuzzerTestOneInput((const uint8_t *)data, 4);
  > }
  > EOF
  >     $CXX $TESTTMP/dummy.cc -o $TESTTMP/dummy \
  >        -fsanitize=fuzzer-no-link,address || return 1
  > }

Try to find a python3-config that's next to our sys.executable. If
that doesn't work, fall back to looking for a global python3-config
and hope that works out for the best.
  $ PYBIN=`"$PYTHON" -c 'import sys, os; print(os.path.dirname(sys.executable))'`
  $ if [ -x "$PYBIN/python3-config" ] ; then
  >   PYTHON_CONFIG="$PYBIN/python3-config"
  > else
  >   PYTHON_CONFIG="`which python3-config`"
  > fi

#if clang-libfuzzer
  $ CXX=clang++ havefuzz || exit 80
  $ $MAKE -s clean all PYTHON_CONFIG="$PYTHON_CONFIG"
#endif
#if no-clang-libfuzzer clang-6.0
  $ CXX=clang++-6.0 havefuzz || exit 80
  $ $MAKE -s clean all CC=clang-6.0 CXX=clang++-6.0 PYTHON_CONFIG="$PYTHON_CONFIG"
#endif
#if no-clang-libfuzzer no-clang-6.0
  $ exit 80
#endif

  $ cd $TESTTMP

Run each fuzzer using dummy.cc as a fake input, to make sure it runs
at all. In the future we should instead unpack the corpus for each
fuzzer and use that instead.

  $ for fuzzer in `ls *_fuzzer | sort` ; do
  >   echo run $fuzzer...
  >   ./$fuzzer dummy.cc > /dev/null 2>&1 
  > done
  run bdiff_fuzzer...
  run dirs_fuzzer...
  run dirstate_fuzzer...
  run fm1readmarkers_fuzzer...
  run fncache_fuzzer...
  run jsonescapeu8fast_fuzzer...
  run manifest_fuzzer...
  run mpatch_fuzzer...
  run revlog_fuzzer...
  run xdiff_fuzzer...

Clean up.
  $ cd $TESTDIR/../contrib/fuzz
  $ $MAKE -s clean