arc: Allow more ABIs in GLIBC_DYNAMIC_LINKER

Enable big-endian suffixed dynamic linker per glibc multi-abi support.

And to avoid a future churn and version pairingi hassles, also allow
arc700 although glibc for ARC currently doesn't support it.

gcc/
xxxx-xx-xx  Vineet Gupta <vgupta@synopsys.com>

       * config/arc/linux.h: GLIBC_DYNAMIC_LINKER support BE/arc700

gcc/ChangeLog

+2020-0-31  Vineet Gupta <vgupta@synopsys.com>
+
+	* config/arc/linux.h: GLIBC_DYNAMIC_LINKER support BE/arc700.
+
 2020-03-31  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>
 
 	* config/arm/arm_mve.h (vaddlvq): Move the polymorphic variant to the

gcc/config/arc/linux.h

@@ -29,7 +29,8 @@ along with GCC; see the file COPYING3.  If not see
     }						\
   while (0)
 
-#define GLIBC_DYNAMIC_LINKER   "/lib/ld-linux-arc.so.2"
+#define GLIBC_DYNAMIC_LINKER					\
+  "/lib/ld-linux-arc%{mbig-endian:eb}%{mcpu=arc700:700}.so.2"
 #define UCLIBC_DYNAMIC_LINKER  "/lib/ld-uClibc.so.0"
 
 /* Note that the default is to link against dynamic libraries, if they are