* nettle: Use fixed --libdir
When building with autoconf 2.69 in Ubuntu 20.04, the build script
fails to detect the library installation location:
+ export LIBNETTLE_A_PATH=
+ LIBNETTLE_A_PATH=
++ realpath ../nettle-with-libgmp-install/lib/libhogweed.a
realpath: ../nettle-with-libgmp-install/lib/libhogweed.a: No such file or directory
Instead of guessing where the static libraries are installed, this
patch makes it always installed in the same location.
* nettle: Use default focal image
When we upgrade to 20.04, python wont be in base-builder and
these projects will fail unless they install it.
Until then, this change should be a noop.
Related: #6180
Daiki Ueno