You can use geninfo in combination with lcov to achieve something similar.
If you have both .gcno and .gcda files available then first we will need to generate .info files.
To generate .info files use :
geninfo "path for .gcda files" -b "path for the source files" -o ./coverage1.info
So this will generate .info for your first test. Similarly, generate .info for all of your tests.
Now you can use lcov to combine these info files and get a combined report. To do that use:
lcov --add-tracefile coverage1.info -a coverage2.info ...coverageN -o merged.info
Now you have combined .info file and you can use genhtml to generate a HTML report for better view.
genhtml merged.info -o CodeCoverage