make it possible to suppress warnings of the vcxproj generator

When the user adds a compiler option that qmake doesn't understand, a
warning message is printed. One can suppress these warnings now by
adding CONFIG+=suppress_vcproj_warnings to the project file.

Task-number: QTBUG-37520
Change-Id: Ieb7ad2c900329e76636047dff85824ea0456f608
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

qmake/generators/win32/msvc_objectmodel.cpp

@@ -312,6 +312,18 @@ static QString vcCommandSeparator()
     return cmdSep;
 }
 
+static void unknownOptionWarning(const char *tool, const char *option)
+{
+    static bool firstCall = true;
+    warn_msg(WarnLogic, "Could not parse %s option '%s'; added to AdditionalOptions.", tool, option);
+    if (firstCall) {
+        firstCall = false;
+        warn_msg(WarnLogic,
+                 "You can suppress these warnings with CONFIG+=suppress_vcproj_warnings.");
+    }
+}
+
+
 // VCCLCompilerTool -------------------------------------------------
 VCCLCompilerTool::VCCLCompilerTool()
     :        AssemblerOutput(asmListingNone),
@@ -1148,7 +1160,8 @@ bool VCCLCompilerTool::parseOption(const char* option)
         break;
     }
     if(!found) {
-        warn_msg(WarnLogic, "Could not parse Compiler option: %s, added as AdditionalOption", option);
+        if (!config->suppressUnknownOptionWarnings)
+            unknownOptionWarning("Compiler", option);
         AdditionalOptions += option;
     }
     return true;
@@ -1743,7 +1756,8 @@ bool VCLinkerTool::parseOption(const char* option)
         break;
     }
     if(!found) {
-        warn_msg(WarnLogic, "Could not parse Linker options: %s, added as AdditionalOption", option);
+        if (!config->suppressUnknownOptionWarnings)
+            unknownOptionWarning("Linker", option);
         AdditionalOptions += option;
     }
     return found;

qmake/generators/win32/msvc_objectmodel.h

@@ -885,6 +885,7 @@ public:
     VCConfiguration();
     ~VCConfiguration(){}
 
+    bool                    suppressUnknownOptionWarnings;
     DotNET                  CompilerVersion;
     bool                    WinRT, WinPhone, WinPhone80;
 

qmake/generators/win32/msvc_vcproj.cpp

@@ -960,6 +960,7 @@ void VcprojGenerator::initConfiguration()
     // - Do this first since main configuration elements may need
     // - to know of certain compiler/linker options
     VCConfiguration &conf = vcProject.Configuration;
+    conf.suppressUnknownOptionWarnings = project->isActiveConfig("suppress_vcproj_warnings");
     conf.CompilerVersion = which_dotnet_version(project->first("MSVC_VER").toLatin1());
 
     initCompilerTool();