Travis: coverage: gcov: process .gnco separately (#2574)

Also uses consistent flags with codecov, i.e. lua53 also with gcov / `#c_code`.

.travis.yml

@@ -125,7 +125,28 @@ install:
     do_codecov_gcov() {
       echo "== do_codecov_gcov in $PWD: $*: =="
       if [ "$DO_COVERAGE" = "codecov" ]; then
-        travis_retry bash /tmp/codecov-bash -X coveragepy -c -F "$1" || return 1
+        # Report coverage for each .gcno file separately.
+        # gcov will create .gcov files for the same source (e.g. for
+        # globalconf.h from awesome.c.gcno and event.c.gcno).
+        i=0
+        set -x
+        (
+          cd build
+          find -path "*/lgi-check.dir" -prune -o \( -name '*.gcno' -print \) | while read -r gcno; do
+            gcov -pb "$gcno"
+
+            mkdir gcov.$(( ++i ))
+            mv *.gcov "gcov.$i"
+
+            # Delete any files for /usr.
+            # They are not relevant and might cause "Invalid path part" errors
+            # with Code Climate.
+            find "gcov.$i" -maxdepth 1 -type f -name '#usr#*.gcov' -delete
+          done
+
+          # Upload to Codecov.
+          travis_retry bash /tmp/codecov-bash -X gcov -X coveragepy -F "$1,${LUANAME//./}"
+        )
       fi
       return 0
     }