domtop: Fix build on mingw

Firstly, there's no sigaction() nor struct sigaction on mingw. We have
to use the one implemented by gnulib (and hence link with gnulib).
Then, for some reason one header file from windows defines ERROR
symbol. Yes it does. Sigh.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

examples/domtop/Makefile.am

@@ -16,9 +16,11 @@
 ## License along with this library.  If not, see
 ## <http://www.gnu.org/licenses/>.
 
-INCLUDES = -I$(top_builddir)/include -I$(top_srcdir)/include
+INCLUDES = -I$(top_builddir)/include -I$(top_srcdir)/include \
+           -I$(top_builddir)/gnulib/lib -I$(top_srcdir)/gnulib/lib \
+           -I$(top_srcdir)
 LDADDS = $(STATIC_BINARIES) $(WARN_CFLAGS) $(top_builddir)/src/libvirt.la \
-	$(COVERAGE_LDFLAGS)
+         $(top_builddir)/gnulib/lib/libgnu.la $(COVERAGE_LDFLAGS)
 
 noinst_PROGRAMS=domtop
 

examples/domtop/domtop.c

@@ -20,6 +20,8 @@
  * Author: Michal Privoznik <mprivozn@redhat.com>
  */
 
+#include <config.h>
+
 #include <errno.h>
 #include <getopt.h>
 #include <libvirt/libvirt.h>
@@ -35,6 +37,21 @@
 static bool debug;
 static bool run_top;
 
+/* On mingw, there's a header file that poisons the well:
+ *
+ *
+ *  CC       domtop.o
+ *domtop.c:40:0: warning: "ERROR" redefined [enabled by default]
+ * #define ERROR(...)                                              \
+ * ^
+ *In file included from /usr/i686-w64-mingw32/sys-root/mingw/include/windows.h:71:0,
+ *                 from /usr/i686-w64-mingw32/sys-root/mingw/include/winsock2.h:23,
+ *                 from ../../gnulib/lib/unistd.h:48,
+ *                 from domtop.c:35:
+ * /usr/i686-w64-mingw32/sys-root/mingw/include/wingdi.h:75:0: note: this is the location of the previous definition
+ * #define ERROR 0
+ */
+#undef ERROR
 #define ERROR(...)                                              \
 do {                                                            \
     fprintf(stderr, "ERROR %s:%d : ", __FUNCTION__, __LINE__);  \