[check-format] exclude subprojects

tools/check-format

@@ -41,7 +41,7 @@ fi
 cd "${ROOTDIR}"
 # Note that the --dry-run and --Werror clang-format arguments require
 # clang-format 10 or higher. See https://reviews.llvm.org/D68554
-find . \( -path '*/\.*' -o -path "./build*" \) -prune -o \
+find . \( -path '*/\.*' -o -path "./subprojects*" -o -path "./build*" \) -prune -o \
 	-type f -regextype posix-extended -regex '.*\.(c|h|cpp|hpp)' -print0 |\
 	tee "${CHECKED_FILES_FILE}" |\
 	xargs --null --max-args=3 --max-procs="${MAX_PROCS}" \