Support passing an environment variable map to child processes.

runtime/bin/process_macos.cc

Index: runtime/bin/process_macos.cc
diff --git a/runtime/bin/process_macos.cc b/runtime/bin/process_macos.cc
index c71aca369b5648eee86817e715ce297f536c3787..f71b461dd36a3bd240ca84d310e9223c33cf1293 100644
--- a/runtime/bin/process_macos.cc
+++ b/runtime/bin/process_macos.cc
@@ -306,6 +306,8 @@ int Process::Start(const char* path,
                    char* arguments[],
                    intptr_t arguments_length,
                    const char* working_directory,
+                   char* environment[],
+                   intptr_t environment_length,
                    intptr_t* in,
                    intptr_t* out,
                    intptr_t* err,
@@ -389,12 +391,21 @@ int Process::Start(const char* path,
   }
 
   char** program_arguments = new char*[arguments_length + 2];
-  program_arguments[0] = const_cast<char *>(path);
+  program_arguments[0] = const_cast<char*>(path);
   for (int i = 0; i < arguments_length; i++) {
     program_arguments[i + 1] = arguments[i];
   }
   program_arguments[arguments_length + 1] = NULL;
 
+  char** program_environment = NULL;
+  if (environment != NULL) {
+    program_environment = new char*[environment_length + 1];
+    for (int i = 0; i < environment_length; i++) {
+      program_environment[i] = environment[i];
+    }
+    program_environment[environment_length] = NULL;
+  }
+
   struct sigaction act;
   bzero(&act, sizeof(act));
   act.sa_sigaction = SigChldHandler;
@@ -449,13 +460,22 @@ int Process::Start(const char* path,
       ReportChildError(exec_control[1]);
     }
 
-    TEMP_FAILURE_RETRY(
-        execvp(path, const_cast<char* const*>(program_arguments)));
+    if (environment != NULL) {
+      TEMP_FAILURE_RETRY(
+          execve(path,
+                 const_cast<char* const*>(program_arguments),
+                 program_environment));
+    } else {
+      TEMP_FAILURE_RETRY(
+          execvp(path, const_cast<char* const*>(program_arguments)));
+    }
     ReportChildError(exec_control[1]);
   }
 
-  // The arguments for the spawned process are not needed any longer.
+  // The arguments and environment for the spawned process are not needed
+  // any longer.
   delete[] program_arguments;
+  delete[] program_environment;
 
   int event_fds[2];
   result = TEMP_FAILURE_RETRY(pipe(event_fds));