selftests, x86: Rework x86 target architecture detection

We currently fail to build on a non-multilib x86_64 target.  We
print a helpful error, but it's nicer to allow the build to succeed.
Fix it and improve cross-compilation support by detecting
architecture support directly and building only the relevant tests.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
diff --git a/tools/testing/selftests/x86/check_cc.sh b/tools/testing/selftests/x86/check_cc.sh
new file mode 100755
index 0000000..172d329
--- /dev/null
+++ b/tools/testing/selftests/x86/check_cc.sh
@@ -0,0 +1,16 @@
+#!/bin/sh
+# check_cc.sh - Helper to test userspace compilation support
+# Copyright (c) 2015 Andrew Lutomirski
+# GPL v2
+
+CC="$1"
+TESTPROG="$2"
+shift 2
+
+if "$CC" -o /dev/null "$TESTPROG" -O0 "$@" 2>/dev/null; then
+    echo 1
+else
+    echo 0
+fi
+
+exit 0