Add to cgminer_CPPFLAGS instead of redefining them.

Conflicts:
	Makefile.am

Makefile.am

@@ -19,10 +19,10 @@ cgminer_LDADD	= $(DLOPEN_FLAGS) @LIBCURL_LIBS@ @JANSSON_LIBS@ @PTHREAD_LIBS@ \
 		  @OPENCL_LIBS@ @NCURSES_LIBS@ @PDCURSES_LIBS@ @WS2_LIBS@ \
 		  @MM_LIBS@ @RT_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@
+cgminer_CPPFLAGS += -I$(top_builddir)/lib -I$(top_srcdir)/lib @OPENCL_FLAGS@
+
+if !HAVE_WINDOWS
+cgminer_CPPFLAGS += @LIBCURL_CFLAGS@
 endif
 
 cgminer_CPPFLAGS += $(ADL_CPPFLAGS)