Fix qbs build with clang.

Properties item considered harmful.

Change-Id: I715b589bdcb6ef9ac35790122a1ba6f009652242
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

qbs/imports/QtcAutotest.qbs

@@ -12,6 +12,7 @@ CppApplication {
                           + FileInfo.relativePath(project.ide_source_tree, sourceDirectory)
 
     cpp.cxxFlags: QtcFunctions.commonCxxFlags(qbs)
+    cpp.linkerFlags: QtcFunctions.commonLinkerFlags(qbs)
     cpp.rpaths: [
         buildDirectory + '/' + project.ide_library_path,
         buildDirectory + '/' + project.ide_library_path + "/..", // OSX

src/libs/ssh/ssh.qbs

@@ -109,12 +109,13 @@ QtcLibrary {
     // For Botan.
     Properties {
         condition: qbs.toolchain.contains("mingw")
-        cpp.cxxFlags: [
+        cpp.cxxFlags: base.concat([
             "-fpermissive",
             "-finline-functions",
             "-Wno-long-long"
-        ]
+        ])
     }
+    cpp.cxxFlags: base
 
     Export {
         Depends { name: "Qt"; submodules: ["widgets", "network"] }