lint: ensure conformity with asmfmt

Run asmfmt suring linting and confirm git repository isn't dirty.
This introduces a developer tools dependency on asmfmt, but not a
runtime dependency.

Updates #8

script/bootstrap

@@ -14,3 +14,6 @@ go get -u github.com/campoy/embedmd
 
 # covertool for merging coverage reports
 go get -u github.com/dlespiau/covertool
+
+# asmfmt for enforcing assembly style
+go get -u github.com/klauspost/asmfmt

script/lint

@@ -4,5 +4,10 @@
 ./script/generate
 test -z "$(git status --porcelain)"
 
+# And it's still clean after asmfmt.
+# Note: we want to confirm we agree with asmfmt without actually depending on it.
+find . -name '*.s' | xargs asmfmt -w
+test -z "$(git status --porcelain)"
+
 # Run suite of golangci-lint checks.
 golangci-lint run