Update the Linux build demo script for flint 3

bin/pip_install_ubuntu.sh

@@ -14,39 +14,16 @@ set -o errexit
 
 # Install runtime and build dependencies
 
-# The commented commands below would attempt to build python-flint against a
-# system installation of Flint and Arb in Ubuntu.
-#
-# Ubuntu 23.04 has Flint 2.9.0 and Arb 2.23.0, so this script might work there
-# (for python-flint 0.4.1). That is untested though (23.04 not available in CI).
-#
-# With Ubuntu 22.04, this will build but then crashes when running the tests.
-# most likely this is because the versions of flint and flint-arb are too old.
-# At the time of writing in Ubuntu 22.04 there is Flint 2.8.4 and Arb 2.22. The
-# main CI tests and wheels for python-flint 0.4.1 are built with Flint 2.9.0
-# and Arb 2.23.0.
-#
-# Link against libflint-arb instead of libarb on Ubuntu
-# export PYTHON_FLINT_LIBFLINT_ARB=1
-# sudo apt-get update
-# sudo apt-get install libflint-dev libflint-arb-dev
-
-
-# Build Flint and Arb manually
-#
 # First install their dependencies and build dependencies
 sudo apt-get update
 sudo apt-get install libgmp-dev libmpfr-dev xz-utils
 
-# Only these *EXACT* versions will work.
-FLINTVER=2.9.0
-ARBVER=2.23.0
+# Only Flint 3 or newer will work.
+FLINTVER=3.0.0-alpha1
 
 # This will default to installing in /usr/local. If you want to install in a
 # non-standard location then configure flint with
 #    ./configure --disable-static --prefix=$PREFIX
-# and arb with
-#    ./configure --disable-static --prefix=$PREFIX --with-flint=$PREFIX
 # If $PREFIX is no in default search paths, then at build time set
 #    export C_INCLUDE_PATH=$PREFIX/include
 # and at runtime set
@@ -55,15 +32,7 @@ ARBVER=2.23.0
 curl -O -L https://www.flintlib.org/flint-$FLINTVER.tar.gz
 tar xf flint-$FLINTVER.tar.gz
 cd flint-$FLINTVER
-  ./configure --disable-static
-  make -j
-  sudo make install
-cd ..
-
-curl -O -L https://github.com/fredrik-johansson/arb/archive/refs/tags/$ARBVER.tar.gz
-mv $ARBVER.tar.gz arb-$ARBVER.tar.gz
-tar xf arb-$ARBVER.tar.gz
-cd arb-$ARBVER
+  ./bootstrap.sh
   ./configure --disable-static
   make -j
   sudo make install