cve-check: add json format
Add an option to output the CVE check in a JSON-based format. This format is easier to parse in software than the original text-based one and allows post-processing by other tools. Output formats are now handed by CVE_CHECK_FORMAT_TEXT and CVE_CHECK_FORMAT_JSON. Both of them are enabled by default. The JSON output format gets generated in a similar way to the text format with the exception of the manifest: appending to JSON arrays requires parsing the file. Because of that we first write JSON fragments and then assemble them in one pass at the end. Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>