[gimp] build: fix header search paths for windres calls (Win32 build).

[Jehan Pagès <jehanp src gnome org>]

commit 5b58cc4b7c1e44d6790573ba12b1fef201253abb
Author: Jehan <jehan girinstud io>
Date:   Mon Feb 12 18:47:43 2018 +0100

    build: fix header search paths for windres calls (Win32 build).
    
    The Win32 build was not taking the new path of git-version.h into
    account and was outputting these errors:
    > ../build/windows/gimp.rc:2:10: fatal error: git-version.h: No such file or directory
    >  #include "git-version.h"
    >           ^~~~~~~~~~~~~~~

 build/windows/gimprc-plug-ins.rule |    1 +
 build/windows/gimprc.rule          |    1 +
 2 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/build/windows/gimprc-plug-ins.rule b/build/windows/gimprc-plug-ins.rule
index 6967e93..eaf059d 100644
--- a/build/windows/gimprc-plug-ins.rule
+++ b/build/windows/gimprc-plug-ins.rule
@@ -10,4 +10,5 @@ GIMPPLUGINRC = $(top_builddir)/build/windows/gimp-plug-ins.rc
                --define TOP_SRCDIR="`echo $(top_srcdir) | sed 's*//*/*'`" \
                -I"`echo $(top_srcdir)/app | sed 's%/\+%/%'`" \
                -I"`echo $(top_builddir)/app | sed 's%/\+%/%'`"\
+               -I"`echo $(top_builddir) | sed 's%/\+%/%'`"\
                $(GIMPPLUGINRC) $@
diff --git a/build/windows/gimprc.rule b/build/windows/gimprc.rule
index 5e3b10d..376bb3a 100644
--- a/build/windows/gimprc.rule
+++ b/build/windows/gimprc.rule
@@ -10,4 +10,5 @@ GIMPAPPRC = $(top_builddir)/build/windows/gimp.rc
                --define TOP_SRCDIR="`echo $(top_srcdir) | sed 's*//*/*'`" \
                -I"`echo $(top_srcdir)/app | sed 's%/\+%/%'`" \
                -I"`echo $(top_builddir)/app | sed 's%/\+%/%'`"\
+               -I"`echo $(top_builddir) | sed 's%/\+%/%'`"\
                $(GIMPAPPRC) $@