ci: remove gcc from prebuilts

gcc is no longer used as part of Hafnium build system.
Remove prebuilts from this tree.

Change-Id: I11e9ac951aaff4a4fcbd9d9033934be9e6402ac8
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
263 files changed
tree: b7f675abb6631a5fbbd8cf14c13fb88cb845dd81
  1. darwin-x64/
  2. generic/
  3. linux-aarch64/
  4. linux-x64/