ci: make env probes non-fatal, swap free for /proc/meminfo

Pipeline #41 died with exit 127 on `free -h` — procps isn't in the
nix-ci image. New info() helper runs the command and ignores the exit
code, so missing tools no longer abort the build. Also switched to
/proc/meminfo since it's always available on Linux.

ci/build.py

@@ -13,6 +13,12 @@ def run(cmd):
         sys.exit(r.returncode)
 
 
+def info(cmd):
+    """Like run(), but tolerant of failure — for non-load-bearing diagnostics."""
+    print(f"+ {cmd}", flush=True)
+    subprocess.run(cmd, shell=True)
+
+
 def build(cmd):
     """Run a `nix build`, streaming stderr live; return stdout (the out path)."""
     print(f"+ {cmd}", flush=True)
@@ -31,10 +37,10 @@ ATTIC_TOKEN = os.environ["ATTIC_TOKEN"]
 print(f"=== Building flake-hub packages for {ARCH} ===")
 
 # Environment context for log readers
-run("nix --version")
-run("uname -a")
-run("df -h /nix 2>/dev/null || df -h /")
-run("free -h")
+info("nix --version")
+info("uname -a")
+info("df -h /nix 2>/dev/null || df -h /")
+info("cat /proc/meminfo | head -3")
 
 # Setup attic
 attic = (