Work around libcurl cflags not working on hacked up mingw installations on windows.

Makefile.am

@@ -26,7 +26,12 @@ cgminer_LDADD	= $(DLOPEN_FLAGS) @LIBCURL_LIBS@ @JANSSON_LIBS@ @PTHREAD_LIBS@ \
 		  @OPENCL_LIBS@ @NCURSES_LIBS@ @PDCURSES_LIBS@ @WS2_LIBS@ \
 		  @UDEV_LIBS@ @USB_LIBS@ \
 		  @MATH_LIBS@ lib/libgnu.a ccan/libccan.a
+
+if HAVE_WINDOWS
+cgminer_CPPFLAGS = -I$(top_builddir)/lib -I$(top_srcdir)/lib @OPENCL_FLAGS@
+else
 cgminer_CPPFLAGS = -I$(top_builddir)/lib -I$(top_srcdir)/lib @OPENCL_FLAGS@ @LIBCURL_CFLAGS@
+endif
 
 # common sources
 cgminer_SOURCES := cgminer.c