Use pkg-config for Leptonica compiler flags

The old settings don't work for cross compilations (wrong include path)
or require setting LIBLEPT_HEADERSDIR. They are used as fallback if
there is no pkg-config configuration.

Signed-off-by: Stefan Weil <sw@weilnetz.de>

configure.ac

@@ -415,30 +415,36 @@ AC_CHECK_TYPES([mbstate_t],,, [#include "wchar.h"])
 # ----------------------------------------
 
 # Check location of leptonica/liblept headers.
-AC_MSG_CHECKING([for leptonica])
 AC_ARG_VAR([LIBLEPT_HEADERSDIR], [Leptonica headers directory])
 
-have_lept=no
-if test "$LIBLEPT_HEADERSDIR" = "" ; then
-  LIBLEPT_HEADERSDIR="/usr/local/include /usr/include /opt/local/include/leptonica"
-fi
-for incd in $LIBLEPT_HEADERSDIR
-do
-  for lept in . leptonica liblept
+PKG_CHECK_MODULES([LEPTONICA], [lept], [have_lept=true], [have_lept=false])
+if !($have_lept); then
+  AC_MSG_CHECKING([for leptonica])
+  if test "$LIBLEPT_HEADERSDIR" = "" ; then
+    LIBLEPT_HEADERSDIR="/usr/local/include /usr/include /opt/local/include/leptonica"
+  fi
+  for incd in $LIBLEPT_HEADERSDIR
   do
-    if test -r "$incd/$lept/allheaders.h" ; then
-      CPPFLAGS="$CPPFLAGS -I$incd/$lept"
-      have_lept=yes
-    fi
+    for lept in . leptonica liblept
+    do
+      if test -r "$incd/$lept/allheaders.h" ; then
+        CPPFLAGS="$CPPFLAGS -I$incd/$lept"
+        have_lept=true
+      fi
+    done
   done
-done
+  if $have_lept; then
+    AC_MSG_RESULT(yes)
+  else
+    AC_MSG_ERROR([leptonica not found])
+  fi
+else
+  CPPFLAGS="$CPPFLAGS $LEPTONICA_CFLAGS"
+fi
 
-if test "$have_lept" = yes ; then
-  AC_MSG_RESULT(yes)
+if $have_lept; then
   AC_CHECK_LIB([lept], [l_generateCIDataForPdf], [],
                [AC_MSG_ERROR([leptonica library with pdf support (>= 1.71) is missing])])
-else
-  AC_MSG_ERROR([leptonica not found])
 fi
 
 AC_MSG_CHECKING([leptonica headers version >= 1.71])