[compiler-rt] Use ld64 flag -lto_library instead of DYLD_LIBRARY_PATH

[thakis]

Summary

Makes

bin/llvm-lit \

projects/compiler-rt/test/profile/Profile-arm64/instrprof-darwin-dead-strip.c

pass on my machine.

Without this change, ld64 complains that the bitcode was generated by LLVM 15
while the reader is 13.1 -- the version of Xcode on my machine. Looks like the
DYLD_LIBRARY_PATH technique isn't working.

-lto_library was added back in ld64-136, which was in Xcode 4.6, which was
released over 10 years ago. So relying on it should be safe by now.

compiler-rt/test/lit.common.cfg.py

for required in ["2.27", "2.30", "2.34"]:
       if ver >= LooseVersion(required):
         config.available_features.add("glibc-" + required)
 
 sancovcc_path = os.path.join(config.llvm_tools_dir, "sancov")
 if os.path.exists(sancovcc_path):
   config.available_features.add("has_sancovcc")
   config.substitutions.append( ("%sancovcc ", sancovcc_path) )
 
+def liblto_path():
+  return os.path.join(config.llvm_shlib_dir, 'libLTO.dylib')
+
 def is_darwin_lto_supported():
-  return os.path.exists(os.path.join(config.llvm_shlib_dir, 'libLTO.dylib'))
+  return os.path.exists(liblto_path())
 
 def is_binutils_lto_supported():
   if not os.path.exists(os.path.join(config.llvm_shlib_dir, 'LLVMgold.so')):
     return False
 
   # We require both ld.bfd and ld.gold exist and support plugins. They are in
   # the same repository 'binutils-gdb' and usually built together.
   for exe in (config.gnu_ld_executable, config.gold_executable):
     ld_cmd = subprocess.Popen([exe, '--help'], stdout=subprocess.PIPE, env={'LANG': 'C'})
     ld_out = ld_cmd.stdout.read().decode()
     ld_cmd.wait()
     if not '-plugin' in ld_out:
       return False
 
   return True
 
 def is_windows_lto_supported():
   return os.path.exists(os.path.join(config.llvm_tools_dir, 'lld-link.exe'))
 
 if config.host_os == 'Darwin' and is_darwin_lto_supported():
   config.lto_supported = True
-  config.lto_launch = ["env", "DYLD_LIBRARY_PATH=" + config.llvm_shlib_dir]
-  config.lto_flags = []
+  config.lto_flags = [ '-Wl,-lto_library,' + liblto_path() ]
 elif config.host_os in ['Linux', 'FreeBSD', 'NetBSD']:
   config.lto_supported = False
   if config.use_lld:
     config.lto_supported = True
   if is_binutils_lto_supported():
     config.available_features.add('binutils_lto')
     config.lto_supported = True
 
   if config.lto_supported:
-    config.lto_launch = []
     if config.use_lld:
       config.lto_flags = ["-fuse-ld=lld"]
     else:
       config.lto_flags = ["-fuse-ld=gold"]
 elif config.host_os == 'Windows' and is_windows_lto_supported():
   config.lto_supported = True
-  config.lto_launch = []
   config.lto_flags = ["-fuse-ld=lld"]
 else:
   config.lto_supported = False
 
 if config.lto_supported:
   config.available_features.add('lto')
   if config.use_thinlto:
     config.available_features.add('thinlto')
if config.expensive_checks:
   config.available_features.add("expensive_checks")
 
 # Propagate the LLD/LTO into the clang config option, so nothing else is needed.
 run_wrapper = []
 target_cflags = [getattr(config, 'target_cflags', None)]
 extra_cflags = []
 
 if config.use_lto and config.lto_supported:
-  run_wrapper += config.lto_launch
   extra_cflags += config.lto_flags
 elif config.use_lto and (not config.lto_supported):
   config.unsupported = True
 
 if config.use_lld and config.has_lld and not config.use_lto:
   extra_cflags += ["-fuse-ld=lld"]
 elif config.use_lld and (not config.has_lld):
   config.unsupported = True

compiler-rt/test/profile/lit.cfg.py

 
 # Clang flags.
 target_cflags=[get_required_attr(config, "target_cflags")]
 clang_cflags = target_cflags + extra_link_flags
 clang_cxxflags = config.cxx_mode_flags + clang_cflags
 
 def build_invocation(compile_flags, with_lto = False):
   lto_flags = []
-  lto_prefix = []
   if with_lto and config.lto_supported:
     lto_flags += config.lto_flags
-    lto_prefix += config.lto_launch
-  return " " + " ".join(lto_prefix + [config.clang] + lto_flags + compile_flags) + " "
+  return " " + " ".join([config.clang] + lto_flags + compile_flags) + " "
 
 def exclude_unsupported_files_for_aix(dirname):
    for filename in os.listdir(dirname):
        source_path = os.path.join( dirname, filename)
        if os.path.isdir(source_path):
            continue
        f = open(source_path, 'r')
        try:

compiler-rt/test/safestack/lit.cfg.py

 # Test suffixes.
 config.suffixes = ['.c', '.cpp', '.m', '.mm', '.ll', '.test']
 
 # Add clang substitutions.
 config.substitutions.append( ("%clang_nosafestack ", config.clang + " -O0 -fno-sanitize=safe-stack ") )
 config.substitutions.append( ("%clang_safestack ", config.clang + " -O0 -fsanitize=safe-stack ") )
 
 if config.lto_supported:
-  config.substitutions.append((r"%clang_lto_safestack ", ' '.join(config.lto_launch + [config.clang] + config.lto_flags + ['-fsanitize=safe-stack '])))
+  config.substitutions.append((r"%clang_lto_safestack ", ' '.join([config.clang] + config.lto_flags + ['-fsanitize=safe-stack '])))
 
 if config.host_os not in ['Linux', 'FreeBSD', 'NetBSD']:
    config.unsupported = True