Check if json.gz files exist, not the gcov version.

Different versions of gcov output different types of files; older versions
output textual data, newer ones output compressed JSON files (the switch
happens in gcov).

"llvm-cov gcov" is supposed to be compatible with gcov, but never outputs compressed JSON files. This means the version check will break if gcov is substituted with this tool.

Checking for the output files created should avoid this issue, and be a more
robust check overall.

Fixes bazelbuild#18874

Closes bazelbuild#18878.

PiperOrigin-RevId: 546901422
Change-Id: Ibcff1310de06bc8bd4637ad8a22f719d7608ea20

Author: c-mita

tools/test/collect_cc_coverage.sh

@@ -150,15 +150,10 @@ function gcov_coverage() {
           # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84879).
           "${GCOV}" -i $COVERAGE_GCOV_OPTIONS -o "$(dirname ${gcda})" "${gcda}"
 
-          # Extract gcov's version: the output of `gcov --version` contains the
-          # version as a set of major-minor-patch numbers, of which we extract
-          # the major version.
-          gcov_major_version=$("${GCOV}" --version | sed -n -E -e 's/^.*\s([0-9]+)\.[0-9]+\.[0-9]+\s?.*$/\1/p')
-
-          # Check the gcov version so we can process the data correctly
-          if [[ $gcov_major_version -ge 9 ]]; then
-              # gcov 9 or higher use a JSON based format for their coverage reports.
-              # The output is generated into multiple files: "$(basename ${gcda}).gcov.json.gz"
+          # Check the type of output: gcov 9 or later outputs compressed JSON
+          # files, but earlier versions of gcov, and all versions of llvm-cov,
+          # do not. These output textual information.
+          if stat --printf='' *.gcov.json.gz > /dev/null 2>&1; then
               # Concatenating JSON documents does not yield a valid document, so they are moved individually
               mv -- *.gcov.json.gz "$(dirname "$output_file")/$(dirname ${gcno_path})"
           else