nios2: Enable Ada run-time build

gcc/
	* config/nios2/nios2.h (nios2_section_threshold): Guard by not
	USED_FOR_TARGET.

From-SVN: r256330

gcc/ChangeLog

+2018-01-08  Sebastian Huber  <sebastian.huber@embedded-brains.de>
+
+	* config/nios2/nios2.h (nios2_section_threshold): Guard by not
+	USED_FOR_TARGET.
+
 2018-01-08  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/83580

gcc/config/nios2/nios2.h

@@ -431,7 +431,7 @@ typedef struct nios2_args
 /* Output before 'small' uninitialized data.  */
 #define SBSS_SECTION_ASM_OP "\t.section\t.sbss"
 
-#ifndef IN_LIBGCC2
+#ifndef USED_FOR_TARGET
 /* Default the definition of "small data" to 8 bytes.  */
 extern unsigned HOST_WIDE_INT nios2_section_threshold;
 #endif