Ship the environment fixed at configure time to the C++ compiler

Use a wrapper script on all platform to ship the environment to
the C++ compiler. This should enable building with Homebrew special
setup and will likely reduce the number of hard corner cases to
solve.

Should unblock #1177.

--
Change-Id: I36f09edaf131f65c730bdd626ce521478ff587c7
Reviewed-on: https://bazel-review.googlesource.com/3560
MOS_MIGRATED_REVID=121462120

tools/cpp/cc_configure.bzl

@@ -50,7 +50,7 @@ def _which(repository_ctx, cmd, default):
   return default if result == None else str(result)
 
 
-def _get_tool_paths(repository_ctx, darwin, cc):
+def _get_tool_paths(repository_ctx, darwin):
   """Compute the path to the various tools."""
   return {k: _which(repository_ctx, k, "/usr/bin/" + k)
           for k in [
@@ -63,7 +63,7 @@ def _get_tool_paths(repository_ctx, darwin, cc):
               "objdump",
               "strip",
           ]} + {
-              "gcc": cc,
+              "gcc": "cc_wrapper.sh",
               "ar": "/usr/bin/libtool"
                     if darwin else _which(repository_ctx, "ar", "/usr/bin/ar")
           }
@@ -289,13 +289,20 @@ def _find_cc(repository_ctx):
   return cc
 
 
-def _tpl(repository_ctx, tpl, substitutions={}):
+def _tpl(repository_ctx, tpl, substitutions={}, out=None):
+  if not out:
+    out = tpl
   repository_ctx.template(
-      tpl,
+      out,
       Label("@bazel_tools//tools/cpp:%s.tpl" % tpl),
       substitutions)
 
 
+def _get_env(repository_ctx):
+  """Convert the environment in a list of export."""
+  env = repository_ctx.os.environ
+  return "\n".join(["export %s='%s'" % (k, env[k]) for k in env])
+
 def _impl(repository_ctx):
   repository_ctx.file("tools/cpp/empty.cc")
   cpu_value = _get_cpu_value(repository_ctx)
@@ -311,17 +318,19 @@ def _impl(repository_ctx):
   else:
     darwin = cpu_value == "darwin"
     cc = _find_cc(repository_ctx)
-    crosstool_cc = "osx_cc_wrapper.sh" if darwin else str(cc)
     darwin = cpu_value == "darwin"
-    tool_paths = _get_tool_paths(repository_ctx, darwin, crosstool_cc)
+    tool_paths = _get_tool_paths(repository_ctx, darwin)
     crosstool_content = _crosstool_content(repository_ctx, cc, cpu_value, darwin)
     opt_content = _opt_content(darwin)
     dbg_content = _dbg_content()
     _tpl(repository_ctx, "BUILD", {
         "%{name}": cpu_value,
         "%{supports_param_files}": "0" if darwin else "1"
     })
-    _tpl(repository_ctx, "osx_cc_wrapper.sh", {"%{cc}": str(cc)})
+    _tpl(repository_ctx,
+        "osx_cc_wrapper.sh" if darwin else "linux_cc_wrapper.sh",
+        {"%{cc}": str(cc), "%{env}": _get_env(repository_ctx)},
+        "cc_wrapper.sh")
     _tpl(repository_ctx, "CROSSTOOL", {
         "%{cpu}": cpu_value,
         "%{content}": _build_crosstool(crosstool_content) + "\n" +

tools/cpp/linux_cc_wrapper.sh.tpl

@@ -0,0 +1,25 @@
+#!/bin/bash
+#
+# Copyright 2015 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Ship the environment to the C++ action
+#
+set -eu
+
+# Set-up the environment
+%{env}
+
+# Call the C++ compiler
+%{cc} "$@"

tools/cpp/osx_cc_wrapper.sh.tpl

@@ -52,6 +52,9 @@ for i in "$@"; do
     fi
 done
 
+# Set-up the environment
+%{env}
+
 # Call the C++ compiler
 %{cc} "$@"