[compiler-rt] [test] Enable the strace_test only if strace is installed

[mgorny]

Summary

Check whether strace is to be found in PATH, and control the strace_test appropriately. This fixes a test failure when strace is not installed.

[kcc]

LGTM,
but please manually verify that the test runs if strace *is* available.

compiler-rt/trunk/test/lsan/TestCases/strace_test.cc

 // Test that lsan reports a proper error when running under strace.
+// REQUIRES: strace
 // RUN: %clangxx_lsan %s -o %t
 // RUN: not strace -o /dev/null %run %t 2>&1 | FileCheck %s
 
 #include <stdio.h>
 #include <stdlib.h>
 
 static volatile void *sink;
 
 int main() {
   sink = malloc(42);
 }
 // CHECK: LeakSanitizer has encountered a fatal error
 // CHECK: HINT: LeakSanitizer does not work under ptrace (strace, gdb, etc)

compiler-rt/trunk/test/lsan/lit.common.cfg

 # -*- Python -*-
 
 # Common configuration for running leak detection tests under LSan/ASan.
 
 import os
 
+import lit.util
+
 def get_required_attr(config, attr_name):
   attr_value = getattr(config, attr_name, None)
   if attr_value == None:
     lit_config.fatal(
       "No attribute %r in test configuration! You may need to run "
       "tests from your build directory or add this attribute "
       "to lit.site.cfg " % attr_name)
   return attr_value

 elif lsan_lit_test_mode == "AddressSanitizer":
   config.name = "LeakSanitizer-AddressSanitizer"
   lsan_cflags = ["-fsanitize=address"]
   config.available_features.add('asan')
 else:
   lit_config.fatal("Unknown LSan test mode: %r" % lsan_lit_test_mode)
 config.name += config.name_suffix
 
+if lit.util.which('strace'):
+  config.available_features.add('strace')
+
 clang_cflags = ["-O0", config.target_cflags] + config.debug_info_flags
 clang_cxxflags = config.cxx_mode_flags + clang_cflags
 lsan_incdir = config.test_source_root + "/../"
 clang_lsan_cflags = clang_cflags + lsan_cflags + ["-I%s" % lsan_incdir]
 clang_lsan_cxxflags = clang_cxxflags + lsan_cflags + ["-I%s" % lsan_incdir]
 
 config.clang_cflags = clang_cflags
 config.clang_cxxflags = clang_cxxflags