fix(pkg/driverbuilder): fixed debian rpi and rt flavors kernel urls fetching

[FedeDP]

What type of PR is this?

/kind bug

Any specific area of the project related to this PR?

/area pkg

What this PR does / why we need it:

This PR fixes support to fetch kernel headers for debian rpi and rt flavors, where the common package has the -$flavor suffix.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Example:

./_output/bin/driverkit docker --target debian --kernelrelease 4.19.0-26-rt-amd64 --kernelversion 1 --output-probe /tmp/mod.o --loglevel debug --builderimage auto:master
level=DEBUG msg="running without a configuration file"
level=DEBUG msg="running with options" output-module="" output-probe=/tmp/mod.o driverversion=master kernelrelease=4.19.0-26-rt-amd64 kernelversion=1 target=debian arch=amd64 kernelurls=[] repo-org=falcosecurity repo-name=libs
level=INFO msg="driver building, it will take a few seconds" processor=docker
level=DEBUG msg="doing a new docker build"
level=DEBUG msg="kernel header url found" url=http://security-cdn.debian.org/pool/main/l/linux/linux-headers-4.19.0-26-rt-amd64_4.19.304-1_amd64.deb
level=DEBUG msg="kernel header url found" url=http://security-cdn.debian.org/pool/main/l/linux/linux-headers-4.19.0-26-common-rt_4.19.304-1_all.deb
level=DEBUG msg="kernel header url found" url=http://mirrors.kernel.org/debian/pool/main/l/linux/linux-kbuild-4.19_4.19.249-2_amd64.deb

As you can see, proper headers are now found and the build succeeds:

level=INFO msg="eBPF probe available" path=/tmp/mod.o

Does this PR introduce a user-facing change?:

NONE

[FedeDP]

On master instead:

./_output/bin/driverkit docker --target debian --kernelrelease 4.19.0-26-rt-amd64 --kernelversion 1 --output-probe /tmp/mod.o --loglevel debug --builderimage auto:master
level=DEBUG msg="running without a configuration file"
level=DEBUG msg="running with options" output-module="" output-probe=/tmp/mod.o driverversion=master kernelrelease=4.19.0-26-rt-amd64 kernelversion=1 target=debian arch=amd64 kernelurls=[] repo-org=falcosecurity repo-name=libs
level=INFO msg="driver building, it will take a few seconds" processor=docker
level=DEBUG msg="doing a new docker build"
level=ERROR msg=exiting err="kernel headers not found"

[FedeDP]

/cc @EXONER4TED

[EXONER4TED]

Very nice!

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: EXONER4TED, FedeDP

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