tools: correctly detect and print FreeBSD OS

Currently the `print_toolchain_versions` script only supports Linux
and Apple macOS when printing OS name and version. This adds support
for FreeBSD.

dist/tools/ci/print_toolchain_versions.sh

@@ -44,6 +44,9 @@ get_os_info() {
     elif [ "$os" = "Darwin" ]; then
         osname="$(sw_vers -productName)"
         osvers="$(sw_vers -productVersion)"
+    elif [ "$os" = "FreeBSD" ]; then
+        osname="$os"
+        osvers="$(freebsd-version)"
     fi
     printf "%s %s" "$osname" "$osvers"
 }