devel: add instructions for using the script

Add instructions for troubleshooting using the script to build an image
and boot it without BIB.

devel/Troubleshooting.md

@@ -0,0 +1,15 @@
+# Troubleshooting build failures
+
+If your container image fails to build using bootc-image-builder, or if it builds successfully but fails to boot, it's often not clear if the problem lies with bootc-image-builder or the container itself.
+
+To test building an image without bootc-image-builder, try the [bootc-install](devel/bootc-install) script in this repository.
+
+**IMPORTANT**
+Before running the script, note that it creates a file called `disk.raw` in the working directory. Make sure this action doesn't overwrite any existing files.
+
+After the disk is created, you can boot test it using qemu. It's best to convert it to a qcow2 image first:
+```
+qemu-img convert -O qcow disk.raw disk.qcow2
+```
+
+You can then follow the [instructions in the README](README.md#running-the-resulting-qcow2-file-on-linux-x86_64) to test that the image boots successfully.