nvptx-none: Define empty GOMP_SELF_SPECS.

Otherwise, offloading with -fopenacc or -fopenmp active will run into:

    x86_64-unknown-linux-gnu-accel-nvptx-none-gcc: error: unrecognized command line option '-pthread'

	gcc/
	* config/nvptx/nvptx.h (GOMP_SELF_SPECS): Define macro.

From-SVN: r220780

gcc/ChangeLog

+2015-02-18  Thomas Schwinge  <thomas@codesourcery.com>
+
+	* config/nvptx/nvptx.h (GOMP_SELF_SPECS): Define macro.
+
 2015-02-18  Andrew Pinski  <apinski@cavium.com>
 	    Naveen H.S  <Naveen.Hurugalawadi@caviumnetworks.com>
 

gcc/config/nvptx/nvptx.h

@@ -33,6 +33,10 @@
       builtin_define ("__nvptx__");		\
     } while (0)
 
+/* Avoid the default in ../../gcc.c, which adds "-pthread", which is not
+   supported for nvptx.  */
+#define GOMP_SELF_SPECS ""
+
 /* Storage Layout.  */
 
 #define BITS_BIG_ENDIAN 0