configure: Fix check for dependencies needed for training

The different checks had set ENABLE_TRAINING unconditionally,
thus overwriting the value from the preceding checks.

So if pango and cairo were available, but icu was missing,
users would still be offered to build the training tools.

The changes for icu and has_cpp11 are not strictly necessary,
but are made here to have uniform code patterns.

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

Author: stweil

configure.ac

@@ -457,34 +457,36 @@ int i = 0;
     [AC_MSG_RESULT(yes)],
     [AC_MSG_FAILURE([leptonica 1.71 or higher is required])])
 
+AM_CONDITIONAL(ENABLE_TRAINING, true)
+
 # Check location of icu headers
 have_icu=false
 AC_CHECK_HEADERS(unicode/uchar.h, have_icu=true, have_icu=false)
 if !($have_icu); then
         AC_MSG_WARN(Training tools WILL NOT be built because of missing icu library.)
         AC_MSG_WARN(Try to install libicu-devel package.)
+        AM_CONDITIONAL(ENABLE_TRAINING, false)
 fi
-AM_CONDITIONAL(ENABLE_TRAINING, $have_icu)
 
 # Check location of pango headers
 PKG_CHECK_MODULES(pango, pango, have_pango=true, have_pango=false)
 if !($have_pango); then
         AC_MSG_WARN(Training tools WILL NOT be built because of missing pango library.)
         AC_MSG_WARN(Try to install libpango1.0-dev package.)
+        AM_CONDITIONAL(ENABLE_TRAINING, false)
 else
       CPPFLAGS="$CPPFLAGS $pango_CFLAGS"
 fi
-AM_CONDITIONAL(ENABLE_TRAINING, $have_pango)
 
 # Check location of cairo headers
 PKG_CHECK_MODULES(cairo, cairo, have_cairo=true, have_cairo=false)
 if !($have_cairo); then
         AC_MSG_WARN(Training tools WILL NOT be built because of missing cairo library.)
         AC_MSG_WARN(Try to install libcairo-dev?? package.)
+        AM_CONDITIONAL(ENABLE_TRAINING, false)
 else
       CPPFLAGS="$CPPFLAGS $cairo_CFLAGS"
 fi
-AM_CONDITIONAL(ENABLE_TRAINING, $have_cairo)
 
 # set c++11 support based on platform/compiler
 if test "x$has_cpp11" = "xyes"; then
@@ -507,7 +509,7 @@ if test "x$has_cpp11" = "xyes"; then
   esac
 else
   AC_MSG_WARN(Training tools WILL NOT be built because of missing c++11 support.)
-  AM_CONDITIONAL(ENABLE_TRAINING, [test "x$has_cpp11" = "xyes"])
+  AM_CONDITIONAL(ENABLE_TRAINING, false)
 fi
 
 # ----------------------------------------