Fixed unit tests on Windows after introduction of GMP to

boost::polygon Voronoi diagram generator by Vojtech.

Fixed Perl bindings on Windows after some "improvement" of the Windows 10
SDK headers, which fail if included from a C++ code using the
extern "C"
clause. Namely, the Windows 10 SDK include for sockets introduces C++ macros
if a "compiled with C++" symbol is provided even if included through
exetrn "C".

deps/CMakeLists.txt

@@ -129,19 +129,6 @@ else()
     include("deps-linux.cmake")
 endif()
 
-# Patch the boost::polygon library with a custom one.
-ExternalProject_Add(dep_boost_polygon
-    EXCLUDE_FROM_ALL ON
-    GIT_REPOSITORY "https://github.com/prusa3d/polygon"
-    GIT_TAG prusaslicer_gmp
-    DEPENDS dep_boost
-    CONFIGURE_COMMAND ""
-    BUILD_COMMAND ""
-    INSTALL_COMMAND ${CMAKE_COMMAND} -E copy_directory
-        "${CMAKE_CURRENT_BINARY_DIR}/dep_boost_polygon-prefix/src/dep_boost_polygon/include/boost/polygon"
-        "${DESTDIR}/usr/local/include/boost/polygon"
-)
-
 set(ZLIB_PKG "")
 if (NOT ZLIB_FOUND) 
     include(ZLIB/ZLIB.cmake)
@@ -170,50 +157,49 @@ if (NOT "${ZLIB_PKG}" STREQUAL "")
     add_dependencies(dep_openexr ${ZLIB_PKG})
 endif ()
 
+set(_dep_list
+    dep_boost
+    dep_tbb
+    dep_libcurl
+    dep_wxWidgets
+    dep_gtest
+    dep_cereal
+    dep_nlopt
+    dep_openvdb
+    dep_OpenCSG
+    dep_CGAL
+    ${PNG_PKG}
+    ${ZLIB_PKG}
+    ${EXPAT_PKG}
+    )
+
+if ("${CMAKE_SIZEOF_VOID_P}" STREQUAL "8")
+    # Patch the boost::polygon library with a custom one.
+    ExternalProject_Add(dep_boost_polygon
+        EXCLUDE_FROM_ALL ON
+        GIT_REPOSITORY "https://github.com/prusa3d/polygon"
+        GIT_TAG prusaslicer_gmp
+        DEPENDS dep_boost
+        CONFIGURE_COMMAND ""
+        BUILD_COMMAND ""
+        INSTALL_COMMAND ${CMAKE_COMMAND} -E copy_directory
+            "${CMAKE_CURRENT_BINARY_DIR}/dep_boost_polygon-prefix/src/dep_boost_polygon/include/boost/polygon"
+            "${DESTDIR}/usr/local/include/boost/polygon"
+    )
+    # Only override boost::Polygon Voronoi implementation with Vojtech's GMP hacks on 64bit platforms.
+    list(APPEND _dep_list "dep_boost_polygon")
+endif ()
+
 if (MSVC)
-
-    add_custom_target(deps ALL
-    DEPENDS
-        dep_boost
-        dep_boost_polygon
-        dep_tbb
-        dep_libcurl
-        dep_wxWidgets
-        dep_gtest
-        dep_cereal
-        dep_nlopt
-        # dep_qhull # Experimental
-        dep_openvdb
-        dep_OpenCSG
-        dep_CGAL
-        ${PNG_PKG}
-        ${ZLIB_PKG}
-        ${EXPAT_PKG}
-    )
-
+    # Experimental
+    #list(APPEND _dep_list "dep_qhull")
 else()
-
-    add_custom_target(deps ALL
-    DEPENDS
-        dep_boost
-        dep_boost_polygon
-        dep_tbb
-        dep_libcurl
-        dep_wxWidgets
-        dep_gtest
-        dep_cereal
-        dep_nlopt
-        dep_qhull
-        dep_openvdb
-        dep_OpenCSG
-        dep_CGAL
-        ${PNG_PKG}
-        ${ZLIB_PKG}
-        ${EXPAT_PKG}
-        # dep_libigl # Not working, static build has different Eigen
-    )
-
+    list(APPEND _dep_list "dep_qhull")
+    # Not working, static build has different Eigen
+    #list(APPEND _dep_list "dep_libigl")
 endif()
 
+add_custom_target(deps ALL DEPENDS ${_dep_list})
+
 # Note: I'm not using any of the LOG_xxx options in ExternalProject_Add() commands
 # because they seem to generate bogus build files (possibly a bug in ExternalProject).