reloc/build_reloc.sh: don't use --no-build-isolation

for downloading the source packages dependecies, we use the
`pip download` command

and we  uses `--no-build-isolation` which mean it doesn't download it's own set of versions,
with using using `--no-binary :all:` to download the source packages

but that's affect also the build dependency which would make it extremely slow,
compile cython from source.

so first pin the cython in the build dependecies, and force the command
download cython always as wheel to avoid building it from source

Fixes: scylladb#78

pyproject.toml

@@ -2,11 +2,11 @@
 requires = [
     "setuptools>=42",
     "wheel",
-    "Cython",
+    "Cython<3",
     "setuptools_scm[toml]>=6.2"
 ]
 build-backend = "setuptools.build_meta"
 
 [tool.setuptools_scm]
 write_to = "pylib/cqlshlib/_version.py"
-tag_regex = '^(?P<prefix>v)?(?P<version>[^\+-]+)(?P<suffix>-scylla)?$'
+tag_regex = '^(?P<prefix>v)?(?P<version>[^\+-]+)(?P<suffix>-scylla)?$'

reloc/build_reloc.sh

@@ -81,7 +81,7 @@ fi
 
 python3 -m pip install ${PIP_EXTRA_OPTS} build==0.10.0 wheel==0.37.1 -t ./build/cqlsh_build
 PYTHONPATH=$(pwd)/build/cqlsh_build python3 -m build -s
-PYTHONPATH=$(pwd)/build/cqlsh_build python3 -m pip download ${PIP_EXTRA_OPTS} --constraint ./requirements.txt --no-binary :all: . --no-build-isolation -d ./build/pypi_packages
+PYTHONPATH=$(pwd)/build/cqlsh_build python3 -m pip download ${PIP_EXTRA_OPTS} --constraint ./requirements.txt --no-binary :all: --only-binary cython . -d ./build/pypi_packages
 
 for package in $(ls ./build/pypi_packages/*.tar.gz)
 do

requirements.txt

@@ -1,5 +1,5 @@
 scylla-driver==3.26.5
 geomet==0.2.1.post1
-PyYAML==6.0
+PyYAML==6.0.1
 click==8.1.3