Fix MIPS BR2_PACKAGE_LINUX_TOOLS_GPIO build

Update mips for snapshot and initrd features.

Document MIPS limitations.

Improve description of test procedure

CONTRIBUTING.adoc

@@ -1,8 +1,25 @@
 = CONTRIBUTING
 
-Testing that should be done for every functional patch:
+== Testing
+
+Testing that should be done for every functional patch.
+
+=== Guest testing
+
+....
+./build
+./run -e '- lkmc_eval="/insrm.sh hello 5;wget -S google.com;poweroff;"' -n
+....
+
+Should:
+
+* boot
+* show `hello.ko` `init` and `exit` messages
+* make a network request
+* shutdown gracefully
+
+TODO automate all of this with a `/test-all.sh` script in guest which outputs to stdout `LKMC_TEST_PASS` or `LKMC_TEST_FAIL` and grep that from host.
+
+=== Host testing
 
-* `./build && ./run` boots
-* `/insrm.sh hello 5`. If a new module was added, use this for that module. Helps catch simple insert remove problems.
-* `wget -O- google.com` for Internet
 * `./run -d` and on another shell `./rungdb start_kernel` should break GDB at `start_kernel`