docs: update usage/custom_pdk_builds

Author: donn

docs/source/usage/custom_pdk_builds.md

@@ -1,45 +1,31 @@
-# Custom-Building PDKs
-The pre-built version of the sky130 PDK variants included with OpenLane includes the following standard cell libraries:
+# Custom PDK Installations
+
+The sky130 PDK variants pulled using `make pdk` include the following standard cell libraries:
+
 * sky130_fd_io
 * sky130_fd_pr
 * sky130_fd_sc_hd
 * sky130_fd_sc_hvl
 * sky130 sram modules
 
-If you need other libraries, you will have to resort to manual builds using [Volare](https://github.com/efabless/volare) as shown below. You will need Git 2.35+ and Docker.
-
-Note that this will take a while, from 20 minutes to an hour depending on your internet speed and compute power.
+If you need other libraries (including the ReRAM library for `sky130B`), you will have to download them using [Volare](https://github.com/efabless/volare) as shown below.
 
 Start a venv shell using `make start-build-env`. You should see a prompt looking kind of like this:
 
 ```bash
 (venv) [user@host openlane]$ 
 ```
 
-First of all, install volare:
-
-```bash
-pip3 install --upgrade --no-cache-dir volare
-```
-
-Then, build the PDK as follows: The `-l` options are the libraries you want to include. For example, to also include `sky130_fd_sc_hs`, you can add `-l sky130_fd_sc_hs` to the default set of libraries using the following command:
+Then, download the libraries as follows: The `-l` options are the libraries you want to include. For example, to download `sky130_fd_sc_hs`, you can add `-l sky130_fd_sc_hs` to your current set of libraries using the following command:
 
 ```bash
-volare build -j$(nproc) --pdk sky130 --clear-build-artifacts --sram -l sky130_fd_io -l sky130_fd_pr -l sky130_fd_sc_hvl -l sky130_fd_sc_hd -l sky130_fd_sc_hs
+volare enable --pdk sky130 -l sky130_fd_sc_hs
 ```
 
 You can also add `-l all` to just include all of them:
 
 ```bash
-volare build -j$(nproc) --pdk sky130 --clear-build-artifacts --sram -l all
-```
-
-Either way, go grab a smoothie. This will take a while.
-
-After it is done, you can then enable the resulting PDK as such:
-
-```bash
-volare enable
+volare enable --pdk sky130 -l all
 ```
 
-Et voila, your custom-built PDK is ready.
+After it is done, your new SCLs are ready to use.