[gimp] configure: default CPPFLAGS_FOR_BUILD to CPPFLAGS on native builds.

[Jehan Pagès <jehanp src gnome org>]

commit 0de259682ed03c14bd55da139a8823f4ef78b33b
Author: Jehan <jehan girinstud io>
Date:   Fri Jun 9 00:40:24 2017 +0200

    configure: default CPPFLAGS_FOR_BUILD to CPPFLAGS on native builds.
    
    Similarly to what I did for CFLAGS and LDFLAGS in commit 20fdb8d, the
    preprocessor flags for build tools should also be correctly defaulted
    and used when building invert-svg.

 configure.ac      |    3 +++
 tools/Makefile.am |    2 +-
 2 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 1b46c5e..150c821 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2143,6 +2143,9 @@ if test "$cross_compiling" != "yes"; then
   if test "x$CFLAGS_FOR_BUILD" = "x"; then
     CFLAGS_FOR_BUILD="$CFLAGS"
   fi
+  if test "x$CPPFLAGS_FOR_BUILD" = "x"; then
+    CPPFLAGS_FOR_BUILD="$CPPFLAGS"
+  fi
 fi
 
 AC_ARG_ENABLE(vector-icons, [  --disable-vector-icons  use raster icons rather than vector ones 
(default=auto)], ,
diff --git a/tools/Makefile.am b/tools/Makefile.am
index d111eb7..aafb81f 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -45,7 +45,7 @@ test_clipboard_LDADD = $(GTK_LIBS)
 
 if ENABLE_VECTOR_ICONS
 invert-svg$(BUILD_EXEEXT): invert-svg.c
-       $(CC_FOR_BUILD) -o $@ $< $(NATIVE_GLIB_LIBS) $(CFLAGS_FOR_BUILD) $(LDFLAGS_FOR_BUILD) 
$(NATIVE_GLIB_CFLAGS)
+       $(CC_FOR_BUILD) -o $@ $< $(NATIVE_GLIB_LIBS) $(CPPFLAGS_FOR_BUILD) $(CFLAGS_FOR_BUILD) 
$(LDFLAGS_FOR_BUILD) $(NATIVE_GLIB_CFLAGS)
 
 
 # compute_svg_viewbox is not built or used because librsvg is just too buggy