Install gcc with aptitude instead of apt-get.

Mirroring workaround from https://github.com/google/amber/pull/844

Bug: none. Fixing kokoro.
Change-Id: I4b57653a539ef78bf037d508dedc47f339c5257d
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/44130
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>