[fusl] Add llvm's lit tool to third_party

third_party/lit/utils/check-coverage

+#!/bin/sh
+
+prog=$(basename $0)
+
+# Expect to be run from the parent lit directory.
+if [ ! -f setup.py ] || [ ! -d lit ]; then
+    printf 1>&2 "%s: expected to be run from base lit directory\n" "$prog"
+    exit 1
+fi
+
+# Parse command line arguments.
+if [ "$1" = "--generate-html" ]; then
+    GENERATE_HTML=1
+    shift
+fi
+
+# If invoked with no arguments, run all the tests.
+if [ $# = "0" ]; then
+    set -- "tests"
+fi
+
+# Check that the active python has been modified to enable coverage in its
+# sitecustomize.
+if ! python -c \
+      'import sitecustomize, sys; sys.exit("coverage" not in dir(sitecustomize))' \
+      >/dev/null 2>&1; then
+    printf 1>&2 "error: active python does not appear to enable coverage in its 'sitecustomize.py'\n"
+    exit 1
+fi
+
+# First, remove any existing coverage data files.
+rm -f tests/.coverage
+find tests -name .coverage.\* -exec rm {} \;
+
+# Next, run the tests.
+lit -sv --param check-coverage=1 "$@"
+
+# Next, move all the data files from subdirectories up.
+find tests/* -name .coverage.\* -exec mv {} tests \;
+
+# Combine all the data files.
+(cd tests && python -m coverage combine)
+
+# Finally, generate the report.
+(cd tests && python -m coverage report)
+
+# Generate the HTML report, if requested.
+if [ ! -z "$GENERATE_HTML" ]; then
+    (cd tests && python -m coverage html)
+fi