VS: Place source-specific AdditionalOptions after target-wide flags

Flags specified in the `COMPILE_FLAGS` source-file property should
be placed after those in target-wide properties so that those on
individual source files can override those on the whole target.
This is already done by most generators but was not implemented
correctly for VS 2010 and above.

Closes: #16400

Help/release/dev/vs-flag-order.rst

@@ -0,0 +1,9 @@
+vs-flag-order
+-------------
+
+* The :ref:`Visual Studio Generators` for VS 2010 and above now place
+  per-source file flags after target-wide flags when they are classified
+  as raw flags with no project file setting (``AdditionalOptions``).
+  This behavior is more consistent with the ordering of flags produced
+  by other generators, and allows flags on more-specific properties
+  (per-source) to override those on more general ones (per-target).

Source/cmVisualStudioGeneratorOptions.cxx

@@ -334,8 +334,9 @@ void cmVisualStudioGeneratorOptions::OutputAdditionalOptions(
       } else {
         fout << "<AdditionalOptions>";
       }
-      fout << cmVisualStudio10GeneratorOptionsEscapeForXML(this->FlagString)
-           << " %(AdditionalOptions)</AdditionalOptions>\n";
+      fout << "%(AdditionalOptions) "
+           << cmVisualStudio10GeneratorOptionsEscapeForXML(this->FlagString)
+           << "</AdditionalOptions>\n";
     } else {
       fout << prefix << "AdditionalOptions=\"";
       fout << cmVisualStudioGeneratorOptionsEscapeForXML(this->FlagString);