Fixed configure.ac to properly detect OpenCL on windows/mingw.

README

@@ -25,7 +25,7 @@ Native WIN32 build instructions (on mingw32, on windows):
 	Install mingw32
 	Install libcurl, copy libcurl.m4 into /mingw/share/aclocal
 	Run:
-	./autogen.sh
+	autoreconf -fvi
 	CFLAGS="-O3 -Wall -msse2 -I<path to AMD APP include>" LDFLAGS="-L<path to AMD APP lib/x86>" ./configure
 	make
 

configure.ac

@@ -43,8 +43,20 @@ case $target in
     ;;
 esac
 
-#AC_CHECK_LIB(OpenCL, clSetKernelArg, OPENCL_LIBS=-lOpenCL)
-OPENCL_LIBS=-lOpenCL
+# Check for OpenCL (the long way needed on mingw32 due to calling conventions)
+AC_MSG_CHECKING([for OpenCL])
+SAVED_LIBS=$LIBS
+LIBS="$LIBS -lOpenCL"
+AC_LINK_IFELSE(
+  [AC_LANG_PROGRAM([[#include <CL/cl.h>]],
+    [[return clSetKernelArg(0, 0, 0, 0); ]])],
+  [AC_MSG_RESULT(yes)
+   AM_CONDITIONAL(HAVE_OPENCL, true)
+   OPENCL_LIBS=-lOpenCL],
+  [AC_MSG_RESULT(no)
+   AM_CONDITIONAL(HAVE_OPENCL, false)])
+LIBS=$SAVED_LIBS
+
 AC_CHECK_LIB(jansson, json_loads, request_jansson=false, request_jansson=true)
 AC_CHECK_LIB(pthread, pthread_create, PTHREAD_LIBS=-lpthread)