Clang: Suppress GCC warning with LLVM 7.0.1

Change-Id: I6de160b42472560a3b33d9a3390b0890eabe9d44
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

qbs/modules/libclang/libclang.qbs

@@ -11,6 +11,7 @@ Module {
 
         property stringList hostOS: qbs.hostOS
         property stringList targetOS: qbs.targetOS
+        property stringList toolchain: qbs.toolchain
 
         property string llvmConfig
         property string llvmVersion
@@ -38,6 +39,8 @@ Module {
             llvmToolingDefines = toolingParams.defines;
             llvmToolingIncludes = toolingParams.includes;
             llvmToolingCxxFlags = toolingParams.cxxFlags;
+            if (toolchain.contains("gcc"))
+                res.push("-Wno-unused-parameter");
             llvmFormattingLibs = ClangFunctions.formattingLibs(llvmConfig, QtcFunctions, targetOS);
             found = llvmConfig && File.exists(llvmIncludeDir.concat("/clang-c/Index.h"));
         }

src/shared/clang/clang_installation.pri

@@ -177,6 +177,7 @@ isEmpty(LLVM_VERSION) {
         GCC_MAJOR_VERSION = $$section(GCC_VERSION, ., 0, 0)
         # GCC8 warns about memset/memcpy for types with copy ctor. Clang has some of these.
         greaterThan(GCC_MAJOR_VERSION, 7):QMAKE_CXXFLAGS += -Wno-class-memaccess
+        QMAKE_CXXFLAGS += -Wno-unused-parameter
     }
 
     LLVM_LIBDIR = $$quote($$system($$llvm_config --libdir, lines))