snap: use apt from the archive instead of compiling

[sergiusens]

Since the introduction of patchelf, it is not necessary to compile apt
anymore, this brings in two important benefits:

• faster builds
• automatic USNs for CVEs where apt is affected

Signed-off-by: Sergio Schvezov sergio.schvezov@canonical.com

• Have you followed the guidelines for contributing?
• Have you signed the CLA?
• If this is a bugfix. Have you checked that there is a bug report open for the issue you are trying to fix on bug reports?
• If this is a new feature. Have you discussed the design on the forum?
• Have you successfully run ./runtests.sh static?
• Have you successfully run ./runtests.sh unit?

---

On bionic the correct apt methods are being used and there is no SIGSEV, ps output follows

sergius+ 30148 30108  6 18:49 pts/3    00:00:04 /snap/snapcraft/x14/usr/bin/python3 /snap/snapcraft/x14/bin/snapcraft pull
sergius+ 30173 30148  0 18:49 pts/3    00:00:00 /snap/snapcraft/x14/usr/lib/apt/methods/http
sergius+ 30174 30148  0 18:49 pts/3    00:00:00 /snap/snapcraft/x14/usr/lib/apt/methods/http
sergius+ 30176 30148  0 18:49 pts/3    00:00:00 /snap/snapcraft/x14/usr/lib/apt/methods/gpgv
sergius+ 30222 30148  1 18:49 pts/3    00:00:00 /snap/snapcraft/x14/usr/lib/apt/methods/store

and the pull finished successfully.

[codecov-io]

Codecov Report

Merging #2156 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #2156      +/-   ##
==========================================
- Coverage   91.32%   91.31%   -0.01%     
==========================================
  Files         193      193              
  Lines       12168    12170       +2     
  Branches     1814     1814              
==========================================
+ Hits        11112    11113       +1     
- Misses        714      716       +2     
+ Partials      342      341       -1

Impacted Files	Coverage Δ
snapcraft/internal/repo/_deb.py	75.93% <0%> (-0.48%)	⬇️
snapcraft/internal/elf.py	83.17% <0%> (+0.32%)	⬆️

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[kyrofa]

Tested it out, seems to work well!