[gexiv2] Revert "build: Use AX_CHECK_ENABLE_DEBUG"

[Jens Georg <jensgeorg src gnome org>]

commit 4738b4632f70d3882e4333406092e94f8aa4ff04
Author: Jens Georg <mail jensge org>
Date:   Sun Mar 19 18:01:05 2017 +0100

    Revert "build: Use AX_CHECK_ENABLE_DEBUG"
    
    This reverts commit 23c77b8d8781e3299e5e6bb05a921344454f3b97.

 configure.ac                |   31 +++++++++--
 m4/ax_check_enable_debug.m4 |  124 -------------------------------------------
 2 files changed, 25 insertions(+), 130 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index f9b10fd..5f61976 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,12 +15,6 @@ AM_INIT_AUTOMAKE([1.11 -Wall no-define foreign dist-xz no-dist-gzip tar-ustar
 AM_MAINTAINER_MODE([enable])
 AM_SILENT_RULES([yes])
 
-##############
-# Debug Mode #
-##############
-
-AX_CHECK_ENABLE_DEBUG([no])
-
 AM_PROG_AR
 LT_PREREQ([2.2])
 LT_INIT([disable-static win32-dll])
@@ -100,6 +94,31 @@ PKG_CHECK_MODULES(EXIV2,
                   ,
                   AC_MSG_ERROR([exiv2 is required. Please install it.]))
 
+##############
+# Debug Mode #
+##############
+
+AC_MSG_CHECKING([debugging mode])
+AC_ARG_ENABLE(debug,
+              [  --enable-debug          enable debug mode [[default=no]]],
+              if eval "test x$enable_debug = xyes"; then
+              DEBUG_CFLAGS="-O0"
+              fi)
+
+if test -n "$DEBUG_CFLAGS"; then
+    AC_MSG_RESULT([yes])
+    if test -z "$CXXFLAGS"; then
+        CXXFLAGS="-O0 -g -pipe -nostdlib -shared"
+    else
+        CXXFLAGS="$DEBUG_CFLAGS $CXXFLAGS"
+    fi
+else
+    AC_MSG_RESULT([no])
+    if test -z "$CXXFLAGS"; then
+        CXXFLAGS="-O2 -g -pipe -nostdlib -shared"
+    fi
+fi
+
 #################
 # Introspection #
 #################