Update wheel build instruction (#8235)

Co-authored-by: Julian Viereck <julian.viereck@gmail.com>
Co-authored-by: Andreas Reich <andreas@rerun.io>

BUILD.md

@@ -84,15 +84,17 @@ pixi run py-fmt
 ```
 
 ### Building an installable Python wheel
-The `py-wheel` command builds a whl file:
+The `py-build-wheels-sdk-only` command builds a whl file:
 ```sh
-pixi run py-wheel --release
+pixi run py-build-wheels-sdk-only
 ```
 Which you can then install in your own Python environment:
 ```sh
-pip install ./target/wheels/*.whl
+pip install ./dist/CURRENT_ARCHITECTURE/*.whl
 ```
 
+**IMPORTANT**: unlike the official wheels, wheels produced by this method do _not_ contain the viewer, so they may only be used for logging purposes.
+
 ## Building and installing the Rerun C++ SDK
 
 On Windows you have to have a system install of Visual Studio 2022 in order to compile the SDK and samples.

pixi.toml

@@ -324,6 +324,10 @@ py-build-notebook = { cmd = "pip install -e rerun_notebook", depends_on = [
   "js-build-base",
 ] }
 
+# Build an installable SDK-only wheel. IMPORTANT: unlike the officially published wheels, the wheel produced by this command does NOT include the viewer.
+# TODO(ab): add a command that produce a complete wheel, including the viewer.
+py-build-wheels-sdk-only = { cmd = "RERUN_ALLOW_MISSING_BIN=1 python scripts/ci/build_and_upload_wheels.py --mode pr --dir ''" }
+
 
 [feature.python-tasks.tasks]