[XRay][compiler-rt][NFC] Expand the PIC test case for XRay

[dberris]

Summary

Here we add a build with -ffunction-sections -fdata-sections and
-Wl,--gc-sections to ensure that we're still able to generate XRay
traces.

This is just adding a test, no functional changes.

test/xray/TestCases/Linux/pic_test.cc

 // Test to check if we handle pic code properly.
 
-// RUN: %clangxx_xray -fxray-instrument -std=c++11 -fpic %s -o %t
+// RUN: %clangxx_xray -fxray-instrument -std=c++11 -ffunction-sections \
+// RUN:     -fdata-sections -fpic -fpie -Wl,--gc-sections %s -o %t
 // RUN: XRAY_OPTIONS="patch_premain=true verbosity=1 xray_logfile_base=pic-test-logging-" %run %t 2>&1 | FileCheck %s
 // After all that, clean up the output xray log.
 //
 // RUN: rm pic-test-logging-*
 
 #include <cstdio>
 
 [[clang::xray_always_instrument]]