Fix X86 flags

Add extra clang cflags, and correct the clang triple for X86 device
builds.

Change-Id: I95abbd0f0f943ebdede905733785ee3659610058
diff --git a/cc/x86_64_device.go b/cc/x86_64_device.go
index ceaf51c..7d9edda 100644
--- a/cc/x86_64_device.go
+++ b/cc/x86_64_device.go
@@ -219,6 +219,10 @@
 	return "${x86_64GccTriple}"
 }
 
+func (t *toolchainX86_64) ToolchainClangLdflags() string {
+	return "${x86_64ToolchainLdflags}"
+}
+
 func (t *toolchainX86_64) ToolchainClangCflags() string {
 	return t.toolchainClangCflags
 }