Added BUILDDIR, a bit of script reworking

Now littlefs's Makefile can work with a custom build directory
for compilation output. Just set the BUILDDIR variable and the Makefile
will take care of the rest.

make BUILDDIR=build size

This makes it very easy to compare builds with different compile-time
configurations or different cross-compilers.

This meant most of code.py's build isolation is no longer needed,
so revisted the scripts and cleaned/tweaked a number of things.

Also bought code.py in line with coverage.py, fixing some of the
inconsistencies that were created while developing these scripts.

One change to note was removing the inline measuring logic, I realized
this feature is unnecessary thanks to GCC's -fkeep-static-functions and
-fno-inline flags.

.github/workflows/status.yml

@@ -46,11 +46,11 @@ jobs:
                   `${{github.event.workflow_run.id}}/jobs" \
                   | jq -er '.jobs[]
                     | select(.name == env.TARGET_JOB)
-                    | .html_url + ((.steps[]
-                      | select(.name == env.TARGET_STEP)
-                      | "#step:\(.number):0") // "")'
-              )
-            )"
+                    | .html_url
+                      + "?check_suite_focus=true"
+                      + ((.steps[]
+                        | select(.name == env.TARGET_STEP)
+                        | "#step:\(.number):0") // "")'))"
             # TODO remove this
             # print for debugging
             echo "$(jq -nc '{