Update integer-gmp's .gitignore file

Note: the .gitignore pattern rules are not that obvious

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>
Handle base et al. specially in foreachLibrary.mk

This adapts the foreachLibrary rule to match the new situation of
base.git, ghc-prim.git, integer-gmp.git, integer-simple.git, and
template-haskell.git being folded into ghc.git (re #9016), and thus
not being mentioned anymore in the `packages` file.

One visible effect of this oversight was that the `clean_libraries`
make target would fail to clean those packages.

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>