vagrant(coverage): drop the gperf files when capturing coverage

Instead of dropping them from the merged report, as recent lcov started
complaining about unknown lines in gperf files:

Capturing coverage data from /systemd-meson-build
geninfo cmd: '/usr/bin/geninfo /systemd-meson-build --output-filename /tmp/tmp.GTvgfBWpZt/build_dir_initial.coverage-info --initial'
Found gcov version: 13.2.1
Using intermediate gcov format
...
geninfo: ERROR: (range) unknown line '114' in /systemd-meson-build/src/basic/af-from-name.gperf: there are only 56 lines in the file.
  Use 'geninfo --filter range' to remove out-of-range lines.
        (use "geninfo --ignore-errors range ..." to bypass this error)

Complements systemd/systemd@9fe1805.

common/utils.sh

@@ -523,7 +523,7 @@ lcov_collect() {
     local build_dir="${2:?}"
     shift 2
 
-    if ! lcov "$@" --directory "$build_dir" --capture --output-file "$output_file"; then
+    if ! lcov "$@" --directory "$build_dir" --capture --exclude "*.gperf" --output-file "$output_file"; then
         _err "Failed to capture coverage data from '$build_dir'"
         return 1
     fi

vagrant/test_scripts/test-arch-coverage.sh

@@ -196,11 +196,7 @@ exectask "lcov_collect-build_dir-final" "lcov_collect $COVERAGE_DIR/build_dir.co
 exectask "coredumpctl_collect" "coredumpctl_collect"
 
 # Merge all "coverage-info" files from the integration tests into one file
-exectask "lcov-merge-coverage" "lcov_merge all-integration-tests.coverage-info $COVERAGE_DIR"
-# Drop *.gperf files from the lcov files
-# See: https://github.com/eddyxu/cpp-coveralls/issues/126#issuecomment-946716583
-#      for reasoning
-exectask "lcov-drop-gperf" "lcov -r all-integration-tests.coverage-info '*.gperf' -o everything.coverage-info"
+exectask "lcov-merge-coverage" "lcov_merge everything.coverage-info $COVERAGE_DIR"
 exectask "lcov-dump-coverage-report" "lcov --list everything.coverage-info"
 # Coveralls repo token is set via the .coveralls.yml configuration file generated
 # in vagrant/vagrant-ci-wrapper.sh