build: use pkg-config for libuuid

Migrate the libuuid detection to use pkg-config via PKG_CHECK_MODULES.
This allows for better portability on systems where library paths may
differ from standard locations.

To align with pkg-config standards (which typically provide include
paths ending in .../uuid), the source code includes are updated from
<uuid/uuid.h> to <uuid.h>.

A fallback mechanism using AC_CHECK_LIB is retained for environments
without pkg-config, ensuring backward compatibility.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>

configure.ac

@@ -84,13 +84,25 @@ AS_IF([test "x$enable_usrmerge" = "xauto"], [
 ])
 
 # Checks for libraries.
-AC_CHECK_LIB([uuid], [uuid_generate], [
-    AC_DEFINE([HAVE_LIBUUID], 1,
-              [Define to 1 if you have the 'uuid' library (-luuid).])
-    AC_SUBST(UUID_LIBS, ["-luuid"])
-    AC_SUBST(UUID_CFLAGS, [""])
-], [
-    AC_MSG_ERROR([UUID library not found])
+m4_ifdef([PKG_CHECK_MODULES], [
+    PKG_CHECK_MODULES([UUID], [uuid], [
+        have_uuid_pkg_config=yes
+        AC_DEFINE([HAVE_LIBUUID], 1,
+                  [Define to 1 if you have the 'uuid' library (-luuid).])
+    ], [have_uuid_pkg_config=no])
+], [have_uuid_pkg_config=no])
+
+# Fall back
+AS_IF([test "x$have_uuid_pkg_config" = "xno"], [
+    AC_CHECK_LIB([uuid], [uuid_generate], [
+        AC_DEFINE([HAVE_LIBUUID], 1,
+                  [Define to 1 if you have the 'uuid' library (-luuid).])
+        AC_SUBST(UUID_LIBS, ["-luuid"])
+        AC_SUBST(UUID_CFLAGS, ["-I/usr/include/uuid"])
+    ], [
+        AC_MSG_ERROR([UUID library not found])
+    ])
+    AC_CHECK_HEADERS([uuid/uuid.h])
 ])
 
 LIB_POSIX_MQ=''

include/cleaner_msg.h

@@ -12,7 +12,7 @@
 #define NILFS_CLEANER_MSG_H
 
 #include <stdint.h>
-#include <uuid/uuid.h>
+#include <uuid.h>
 #include "nilfs_cleaner.h"
 
 #define NILFS_CLEANER_PRIO_HIGH		1

lib/cleaner_ctl.c

@@ -74,7 +74,7 @@
 #include <stdarg.h>
 #include <errno.h>
 #include <assert.h>
-#include <uuid/uuid.h>
+#include <uuid.h>
 
 #include "nilfs_cleaner.h"
 #include "cleaner_exec.h"

sbin/cleanerd.c

@@ -73,7 +73,7 @@
 #include <signal.h>
 #include <setjmp.h>
 #include <assert.h>
-#include <uuid/uuid.h>
+#include <uuid.h>
 #include <linux/nilfs2_ondisk.h>  /* NILFS_MIN_NRSVSEGS */
 #include "nilfs.h"
 #include "compat.h"

sbin/mkfs.c

@@ -50,7 +50,7 @@
 #include <sys/wait.h>
 #endif	/* HAVE_SYS_WAIT_H */
 
-#include <uuid/uuid.h>
+#include <uuid.h>
 
 #if HAVE_STRING_H
 #include <string.h>