fix: update libevent pattern for android (#5441)

[jackulau]

Add pattern to detect libevent version in Android libraries where the version string format differs from standard Linux binaries.

• Add FILENAME_PATTERNS to match libevent library files
• Add VERSION_PATTERN to match Android format where version appears before "Active events:" diagnostic string
• Add test case for Android libevent format

Summary

Addresses #5441 - Android libevent library not detected by CVE-bin-tool.

• Added FILENAME_PATTERNS to match libevent library files
• Added new VERSION_PATTERN to detect version in Android binaries where the version string is standalone
• Added test case for Android libevent format

Details

The existing patterns required the string libevent using: to be adjacent to the version, which is not the case in Android binaries. In Android's libevent.so, the version string 2.1.8-stable appears standalone between other diagnostic strings.

The new pattern:

r"([0-9]+\.[0-9]+\.[0-9]+)-stable\r?\nActive events:"

Matches:

• Confirmed pattern detects version 2.1.8

Test plan

• Run pytest -k libevent to validate test cases

[ffontaine]

Thanks for this PR, first you shall add a Signed-off-by tag through git commit -s to fix DCO test.

Moreover, libevent must be added to other_products for 1 libreswan package and 2 tor packages to fix the following errors:

FAILED test/test_scanner.py::TestScanner::test_version_in_package[http://rpmfind.net/linux/fedora/linux/development/rawhide/Everything/aarch64/os/Packages/l/-libreswan-5.1-5.fc42.aarch64.rpm-libreswan-5.1-other_products640] - AssertionError: libevent found in libreswan-5.1-5.fc42.aarch64.rpm. If that's expected, make sure to add libevent to the expected list of other_products.
assert 'libevent' not in {'libevent', 'libreswan'}
FAILED test/test_scanner.py::TestScanner::test_version_in_package[http://rpmfind.net/linux/mageia/distrib/cauldron/aarch64/media/core/release/-tor-0.4.7.10-2.mga9.aarch64.rpm-tor-0.4.7.10-other_products1251] - AssertionError: libevent found in tor-0.4.7.10-2.mga9.aarch64.rpm. If that's expected, make sure to add libevent to the expected list of other_products.
assert 'libevent' not in {'libevent', 'tor'}
FAILED test/test_scanner.py::TestScanner::test_version_in_package[http://ftp.debian.org/debian/pool/main/t/tor/-tor_0.2.9.16-1_arm64.deb-tor-0.2.9.16-other_products1252] - AssertionError: libevent found in tor_0.2.9.16-1_arm64.deb. If that's expected, make sure to add libevent to the expected list of other_products.
assert 'libevent' not in {'libevent', 'tor'}

[ffontaine]

Moreover, you can remove x00 from VERSION_PATTERNS and version_strings as it will be automatically ignored by cve-bin-tool