[gimp/meson] Fix missing cflags, add guard for windows build

[Félix Piédallu <fpiedallu src gnome org>]

commit 3f62a8ce2f1a7729b8f79d8370fce9a935ee07b2
Author: Félix Piédallu <felix piedallu me>
Date:   Mon Feb 12 23:52:14 2018 +0100

    Fix missing cflags, add guard for windows build

 libgimpbase/gimputils.c |    2 ++
 meson.build             |    5 ++---
 2 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/libgimpbase/gimputils.c b/libgimpbase/gimputils.c
index 568346e..7929ef0 100644
--- a/libgimpbase/gimputils.c
+++ b/libgimpbase/gimputils.c
@@ -25,7 +25,9 @@
 #include <string.h>
 #include <stdio.h>
 
+#ifdef HAVE_SYS_WAIT_H
 #include <sys/wait.h>
+#endif
 
 #ifdef PLATFORM_OSX
 #include <AppKit/AppKit.h>
diff --git a/meson.build b/meson.build
index b23c542..7629d15 100644
--- a/meson.build
+++ b/meson.build
@@ -309,9 +309,8 @@ if have_screenshot and not have_xlibs
   error('Screenshot requires x libs')
 endif
 
-if not cc.has_header('execinfo.h')
-  error('The compiler does not provide required header "execinfo.h"')
-endif
+conf.set('HAVE_EXECINFO_H', cc.has_header('execinfo.h'))
+conf.set('HAVE_SYS_WAIT_H', cc.has_header('sys/wait.h'))
 ################################################################################
 # MIME types
 # The list of MIME types that are supported by plug-ins