Start to fusl toolchain

fusl/tools/populate_crt.py

Index: fusl/tools/populate_crt.py
diff --git a/fusl/tools/populate_crt.py b/fusl/tools/populate_crt.py
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+++ b/fusl/tools/populate_crt.py
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+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os.path
+import shutil
+import subprocess
+import sys
+
+
+"""Populate the compiler-provided portions of the fusl sysroot.
+
+In particular, crtbegin, ocrtend.o,libgcc.a, and so on must be copied
+from the host sysroot to our sysroot.
+"""
+
+def parse_clang_dirs(clang):
+  """Parse the output of |clang -print-search-dirs|.
+
+  This is used to find library search paths. One line of the output
+  is formatted something like:
+
+  libraries: =/usr/lib/gcc/4.8:/lib:/usr/lib
+
+  This functions strips the 'libraries: =' prefix and splits on the
+  colon, returning the list:
+
+  [ '/usr/lib/gcc/4.8', '/lib', '/usr/lib' ]
+  """
+
+  clang_search_dirs = subprocess.check_output([clang, '-print-search-dirs'])
+
+  library_line = None
+  library_line_prefix = 'libraries: ='
+  for line in clang_search_dirs.split('\n'):
+    if line.startswith(library_line_prefix):
+      prefix_length = len(library_line_prefix)
+      library_line = line[prefix_length:]
+      break
+  assert(library_line)
+  return library_line.split(':')
+
+
+def try_populate(artifact, library_paths, target):
+  """Returns whether we found the artifact and copied it."""
+
+  for library_path in library_paths:
+    source = os.path.join(library_path, artifact)
+    if not os.path.isfile(source):
+      continue
+    shutil.copy(source, target)
+    return True
+
+  return False
+
+
+def main():
+  clang = sys.argv[1]
+  target = sys.argv[2]
+  artifacts = sys.argv[3:]
+  assert(len(artifacts))
+
+  library_paths = parse_clang_dirs(clang)
+
+  for artifact in artifacts:
+    if not try_populate(artifact, library_paths, target):
+      print('Unable to locate %s in any of the following paths: %s' %
+            (artifact, library_paths))
+      exit(1)
+
+
+if __name__ == '__main__':
+  main()