Make the ninja generator handle symlinked paths correctly.

pylib/gyp/generator/ninja.py

Index: pylib/gyp/generator/ninja.py
diff --git a/pylib/gyp/generator/ninja.py b/pylib/gyp/generator/ninja.py
index 51c288b2164ff2e2b7aa337302ee946764b17be2..fe64461a34ed8ad9d1765d042709811e6dd3153f 100644
--- a/pylib/gyp/generator/ninja.py
+++ b/pylib/gyp/generator/ninja.py
@@ -1672,7 +1672,7 @@ def CommandWithWrapper(cmd, wrappers, prog):
 
 def GetDefaultConcurrentLinks():
   """Returns a best-guess for a number of concurrent links."""
-  pool_size = int(os.getenv('GYP_LINK_CONCURRENCY', 0))
+  pool_size = int(os.environ.get('GYP_LINK_CONCURRENCY', 0))
   if pool_size:
     return pool_size
 
@@ -1699,7 +1699,7 @@ def GetDefaultConcurrentLinks():
     # VS 2015 uses 20% more working set than VS 2013 and can consume all RAM
     # on a 64 GB machine.
     mem_limit = max(1, stat.ullTotalPhys / (5 * (2 ** 30)))  # total / 5GB
-    hard_cap = max(1, int(os.getenv('GYP_LINK_CONCURRENCY_MAX', 2**32)))
+    hard_cap = max(1, int(os.environ.get('GYP_LINK_CONCURRENCY_MAX', 2**32)))
     return min(mem_limit, hard_cap)
   elif sys.platform.startswith('linux'):
     if os.path.exists("/proc/meminfo"):
@@ -2277,7 +2277,11 @@ def GenerateOutputForConfig(target_list, target_dicts, data, params,
     if flavor == 'mac':
       gyp.xcode_emulation.MergeGlobalXcodeSettingsToSpec(data[build_file], spec)
 
-    build_file = gyp.common.RelativePath(build_file, options.toplevel_dir)
+    # If build_file is a symlink, we must not follow it because there's a chance
+    # it could point to a path above toplevel_dir, and we cannot correctly deal
+    # with that case at the moment.
+    build_file = gyp.common.RelativePath(build_file, options.toplevel_dir,
+                                         False)
 
     qualified_target_for_hash = gyp.common.QualifiedTarget(build_file, name,
                                                            toolset)