Revert "add_custom_command: Diagnose MAIN_DEPENDENCY limitation."

This reverts commit 242c3966 (add_custom_command: Diagnose
MAIN_DEPENDENCY limitation, 2015-03-09) and the follow up commit
b372a99a (UseSWIG: Do not use MAIN_DEPENDENCY on custom commands,
2015-03-26).

I misdiagnosed the underlying issue that prompted creation of policy CMP0057.
The actual issue surfaces when a single custom command's MAIN_DEPENDENCY
is listed in more than one target; this issue will have to be addressed
independently.

1 files changed, 0 insertions, 27 deletions

diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index c77a90c..0f0cb34 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -877,33 +877,6 @@ cmMakefile::AddCustomCommandToOutput(const std::vector<std::string>& outputs,
         }
       else
         {
-        std::ostringstream e;
-        cmake::MessageType messageType = cmake::AUTHOR_WARNING;
-        bool issueMessage = false;
-
-        switch(this->GetPolicyStatus(cmPolicies::CMP0057))
-          {
-          case cmPolicies::WARN:
-            e << (this->GetPolicies()->
-              GetPolicyWarning(cmPolicies::CMP0057)) << "\n";
-            issueMessage = true;
-          case cmPolicies::OLD:
-            break;
-          case cmPolicies::NEW:
-          case cmPolicies::REQUIRED_IF_USED:
-          case cmPolicies::REQUIRED_ALWAYS:
-            issueMessage = true;
-            messageType = cmake::FATAL_ERROR;
-            break;
-          }
-
-        if(issueMessage)
-          {
-          e << "\"" << main_dependency << "\" can only be specified as a "
-            "custom command MAIN_DEPENDENCY once.";
-          IssueMessage(messageType, e.str());
-          }
-
         // The existing custom command is different.  We need to
         // generate a rule file for this new command.
         file = 0;