separated working in a container from the build page

docs/how-to/build.md

@@ -1,4 +1,4 @@
-# How to build the PandA image
+# How to build the PandA boot image
 
 ## Prerequisites
 
@@ -64,47 +64,6 @@
 
    A `boot-<machine>.zip` file is created in the current directory.
 
-## Running in a container manually
-
-For development work (e.g. FPGA builds requiring Vivado), a
-`pandablocks-dev-container` image is published on the GitHub Container
-Registry.
-
-Pull it:
-
-```bash
-docker pull ghcr.io/pandablocks/pandablocks-dev-container:latest
-```
-
-Use a numbered tag instead of `latest` to pin a specific release.
-
-Create three host directories:
-
-- `REPO_DIR` — containing all PandA repositories
-- `VIVADO_DIR` — containing a Vivado installation
-- `BUILD_DIR` — an empty scratch directory
-
-Run the container with those directories mounted:
-
-```bash
-docker run --rm --net=host -it \
-  -v REPO_DIR:/repos:Z \
-  -v BUILD_DIR:/build:Z \
-  -v VIVADO_DIR:/scratch/Xilinx \
-  ghcr.io/pandablocks/pandablocks-dev-container /bin/bash
-```
-
-:::{note}
-The mount path for Vivado inside the container must match your local path.
-For example, if Vivado is at `/FPGA/Xilinx` on the host use
-`-v /FPGA/Xilinx:/FPGA/Xilinx` and edit `CONFIG` accordingly.
-:::
-
-In each repository inside the container:
-
-```bash
-cp CONFIG.example CONFIG
-```
 
 ## Output files
 
@@ -120,3 +79,5 @@ cp CONFIG.example CONFIG
 Copy these files to the SD card and insert it in the target; the system will
 boot normally.  On the first boot of a pandabox you will be prompted for a MAC
 address.
+
+To build the FPGA bitstream that can be used to make the firmware, see [PandABlocks-FPGA documentation](https://pandablocks.github.io/PandABlocks-FPGA/docs/)