https://github.com/storaged-project/libblockdev/pull/1111

From bc1fa125aed4ba6e12a19bd00bb75be21b96f44a Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Wed, 18 Jun 2025 04:27:30 +0100
Subject: [PATCH] configure.ac: fix bashism

configure scripts run with a #!/bin/sh shebang which means they should work
with a POSIX shell, so avoid using '+=' which is a bashism.
---
 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/configure.ac
+++ b/configure.ac
@@ -310,7 +310,7 @@ AS_IF([test "x$with_smart" != "xno"],
 
 AS_IF([test "x$with_smart" != "xno"],
       [SAVED_CFLAGS=$CFLAGS
-       CFLAGS+=" -I$drivedb_path"
+       CFLAGS="${CFLAGS} -I$drivedb_path"
        AC_MSG_CHECKING([for drivedb.h presence])
        AC_COMPILE_IFELSE(
            [AC_LANG_PROGRAM([