[glibmm] Reintroduce CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS (microsoft#6550)

(partially reverts change discussed in microsoft#5937)

ports/glibmm/CMakeLists.txt

@@ -40,6 +40,11 @@ if(APPLE)
   link_libraries(${COREFOUNDATION_LIBRARY} ${CORESERVICES_LIBRARY} ${FOUNDATION_LIBRARY})
 endif()
 
+# A hacky solution for building Windows DLLs from sources ported from Linux.
+# The cleaner approach would be to manually add __declspec(dllexport) to all public symbols in the header files or
+# construct a .def file.
+set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS TRUE)
+
 if(BUILD_SHARED_LIBS)
     add_definitions(-DGLIBMM_DLL -DGIOMM_DLL)
 else()

ports/glibmm/CONTROL

@@ -1,4 +1,4 @@
-Source: glibmm
-Version: 2.52.1-8
-Description: This is glibmm, a C++ API for parts of glib that are useful for C++. See http://www.gtkmm.org.
-Build-Depends: zlib, pcre, libffi, gettext, libiconv, glib, libsigcpp
+Source: glibmm
+Version: 2.52.1-9
+Description: This is glibmm, a C++ API for parts of glib that are useful for C++. See http://www.gtkmm.org.
+Build-Depends: zlib, pcre, libffi, gettext, libiconv, glib, libsigcpp

ports/glibmm/portfile.cmake

@@ -5,7 +5,10 @@ if (VCPKG_CMAKE_SYSTEM_NAME STREQUAL WindowsStore)
     message(FATAL_ERROR "Error: UWP builds are currently not supported.")
 endif()
 
-vcpkg_check_linkage(ONLY_STATIC_LIBRARY)
+# This library itself would would as static library, but it is used by gtkmm, atkmm & pangomm which are all set to ONLY_DYNAMIC LIBRARY
+# Having multiple dynamic libaries linking the same static library causes multiple copies of its static data to be present in the executable
+# leading to confusing and hard-to-debug runtime effects.
+vcpkg_check_linkage(ONLY_DYNAMIC_LIBRARY)
 
 set(SOURCE_PATH ${CURRENT_BUILDTREES_DIR}/src/glibmm-2.52.1)
 vcpkg_download_distfile(ARCHIVE