Configure: use ELFv2 ABI on some ppc64 big endian systems

If _CALL_ELF is defined to be 2, it's an ELFv2 system.
Conditionally switch to the v2 perlasm scheme.

Configure

@@ -1403,14 +1403,18 @@ if ($target{sys_id} ne "")
         push @{$config{openssl_sys_defines}}, "OPENSSL_SYS_$target{sys_id}";
         }
 
-unless ($disabled{asm}) {
-}
-
 my %predefined_C = compiler_predefined($config{CROSS_COMPILE}.$config{CC});
 my %predefined_CXX = $config{CXX}
     ? compiler_predefined($config{CROSS_COMPILE}.$config{CXX})
     : ();
 
+unless ($disabled{asm}) {
+    # big endian systems can use ELFv2 ABI
+    if ($target eq "linux-ppc64") {
+        $target{perlasm_scheme} = "linux64v2" if ($predefined_C{_CALL_ELF} == 2);
+    }
+}
+
 # Check for makedepend capabilities.
 if (!$disabled{makedepend}) {
     if ($config{target} =~ /^(VC|vms)-/) {