Run objcopy --update-section test only on ELF targets

* binutils-all/update-section.exp: Only run on ELF targets.

binutils/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2015-03-11  Alan Modra  <amodra@gmail.com>
+
+	* binutils-all/update-section.exp: Only run on ELF targets.
+
 2015-03-03  Jiong Wang  <jiong.wang@arm.com>
 
 	* binutils-all/arm/rvct_symbol.s: New testcase.

binutils/testsuite/binutils-all/update-section.exp

@@ -18,6 +18,11 @@ if { [is_remote host] } then {
     return
 }
 
+# These tests use ELF .section directives
+if ![is_elf_format] {
+    return
+}
+
 send_user "Version [binutil_version $OBJCOPY]"
 
 proc do_assemble {srcfile} {