Fixed link time warnings on MacOS

MacOS' linker dislikes local static variables that are used
in two separate libraries. Removing them from the header files
fixes all the warnings.

Bug b/chromium:907088

Change-Id: I7b8ed44bf9a3180489a7407980740fd3f3863046
Reviewed-on: https://swiftshader-review.googlesource.com/c/22889
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/OpenGL/libGLESv2/libGLESv2.vcxproj

diff --git a/src/OpenGL/libGLESv2/libGLESv2.vcxproj b/src/OpenGL/libGLESv2/libGLESv2.vcxproj
index 5c0e73e..8748629 100644
--- a/src/OpenGL/libGLESv2/libGLESv2.vcxproj
+++ b/src/OpenGL/libGLESv2/libGLESv2.vcxproj
@@ -350,6 +350,7 @@
     </ResourceCompile>

   </ItemDefinitionGroup>

   <ItemGroup>

+    <ClCompile Include="..\..\Common\SharedLibrary.cpp" />

     <ClCompile Include="..\common\Image.cpp" />

     <ClCompile Include="..\common\Object.cpp" />

     <ClCompile Include="Buffer.cpp" />