[XRay][compiler-rt] Require build-in-tree and x86_64-linux.

The quiet-start.cc test currently fails for arm (and potentially other
platforms). This change limits it to x86_64-linux.

Follow-up to D35789.

llvm-svn: 309538

compiler-rt/test/xray/TestCases/Linux/quiet-start.cc

@@ -7,6 +7,10 @@
 // RUN: XRAY_OPTIONS="patch_premain=true verbosity=0" %run %t 2>&1 | \
 // RUN:    FileCheck %s --check-prefix QUIET
 // RUN: XRAY_OPTIONS="" %run %t 2>&1 | FileCheck %s --check-prefix DEFAULT
+//
+// FIXME: Understand how to make this work on other platforms
+// REQUIRES: built-in-llvm-tree
+// REQRUIES: x86_64-linux
 #include <iostream>
 
 using namespace std;