ci: Add a codestyle.sh

This matches what we do in rpm-ostree.  Move the `glnx_fd_close`
bits out of `make syntax-check` in preparation for dropping that.

ci/codestyle.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# Tests that validate structure of the source code;
+# can be run without building it.
+set -euo pipefail
+
+# Don't hard require Rust
+if command -v cargo >/dev/null; then
+echo -n "checking rustfmt... "
+for crate in $(find -iname Cargo.toml); do
+    if ! cargo fmt --manifest-path ${crate} -- --check; then
+        echo "cargo fmt failed; run: cd $(dirname ${crate}) && cargo fmt" 1>&2
+        exit 1
+    fi
+done
+echo "ok"
+fi
+
+echo -n 'grep-based static analysis... '
+patterns=(glnx_fd_close)
+for pat in "${patterns[@]}"; do
+    if git grep "${pat}" | grep -v codestyle\.sh; then
+        echo "Files matched prohibited pattern: ${pat}" 1>&2
+        exit 1
+    fi
+done
+echo ok

ci/gh-build.sh

@@ -26,6 +26,9 @@
 set -euo pipefail
 set -x
 
+# First, basic static analysis
+./ci/codestyle.sh
+
 NOCONFIGURE=1 ./autogen.sh
 
 srcdir="$(pwd)"