[XRay] Run tests inside bootstrapping build

COMPILER_RT_STANDALONE_BUILD is set when doing a bootstrapping build
through LLVM_ENABLE_RUNTIMES with the CMake source directory being in
llvm/. This patch changes the XRay tests to also detect that we have
LLVM sources and the llvm-xray tool if we are in a bootstrapping build
through the use of the LLVM_TREE_AVAILABLE variable which is set in
runtimes/CMakeLists.txt.

Author: boomanaiden154

compiler-rt/test/xray/lit.site.cfg.py.in

@@ -5,7 +5,7 @@ config.name_suffix = "@XRAY_TEST_CONFIG_SUFFIX@"
 config.xray_lit_source_dir = "@XRAY_LIT_SOURCE_DIR@"
 config.target_cflags = "@XRAY_TEST_TARGET_CFLAGS@"
 config.target_arch = "@XRAY_TEST_TARGET_ARCH@"
-config.built_with_llvm = ("@COMPILER_RT_STANDALONE_BUILD@" != "TRUE")
+config.built_with_llvm = ("@COMPILER_RT_STANDALONE_BUILD AND NOT LLVM_TREE_AVAILABLE@" != "TRUE")
 
 # TODO: Look into whether we can run a capability test on the standalone build to
 # see whether it can run 'llvm-xray convert' instead of turning off tests for a