Clang: Use compiler specific undefine option

libclang generated:

    warning: /U__cpp_aggregate_nsdmi: 'linker' input unused [-Wunused-command-line-argument]
    warning: /U__cpp_alias_templates: 'linker' input unused [-Wunused-command-line-argument]
    ...

It needs -U.

Change-Id: Ibbd2f97e6f806215e3008803f57608b9b6b4c641
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

1 files changed, 6 insertions, 1 deletions

diff --git a/src/plugins/cpptools/compileroptionsbuilder.cpp b/src/plugins/cpptools/compileroptionsbuilder.cpp
index 6f2991fea0..f3b89c27f6 100644
--- a/src/plugins/cpptools/compileroptionsbuilder.cpp
+++ b/src/plugins/cpptools/compileroptionsbuilder.cpp
@@ -342,7 +342,7 @@ void CompilerOptionsBuilder::undefineCppLanguageFeatureMacrosForMsvc2015()
         // Undefine the language feature macros that are pre-defined in clang-cl 3.8.0,
         // but not in MSVC2015's cl.exe.
         foreach (const QString &macroName, languageFeatureMacros())
-            m_options.append(QLatin1String("/U") + macroName);
+            m_options.append(undefineOption() + macroName);
     }
 }
 
@@ -364,6 +364,11 @@ QString CompilerOptionsBuilder::defineOption() const
     return QLatin1String("-D");
 }
 
+QString CompilerOptionsBuilder::undefineOption() const
+{
+    return QLatin1String("-U");
+}
+
 static bool isGccOrMinGwToolchain(const Core::Id &toolchainType)
 {
     return toolchainType == ProjectExplorer::Constants::GCC_TOOLCHAIN_TYPEID