build: borrow CMake modules from qt-gstreamer for Linux compatibility

Almost certainly breaks Windows compat, but will need to update it anyways to work with the newer GStreamer SDK.

cmake/modules/FindGLIB2.cmake

@@ -0,0 +1,64 @@
+# - Try to find the GLIB2 libraries
+# Once done this will define
+#
+#  GLIB2_FOUND - system has glib2
+#  GLIB2_INCLUDE_DIR - the glib2 include directory
+#  GLIB2_LIBRARIES - glib2 library
+
+# Copyright (c) 2008 Laurent Montel, <montel@kde.org>
+#
+# Redistribution and use is allowed according to the terms of the BSD license.
+# For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+
+
+if(GLIB2_INCLUDE_DIR AND GLIB2_LIBRARIES)
+    # Already in cache, be silent
+    set(GLIB2_FIND_QUIETLY TRUE)
+endif(GLIB2_INCLUDE_DIR AND GLIB2_LIBRARIES)
+
+if (NOT WIN32)
+   find_package(PkgConfig REQUIRED)
+   pkg_check_modules(PKG_GLIB REQUIRED glib-2.0)
+endif(NOT WIN32)
+
+find_path(GLIB2_MAIN_INCLUDE_DIR glib.h
+          PATH_SUFFIXES glib-2.0
+          HINTS ${PKG_GLIB_INCLUDE_DIRS} ${PKG_GLIB_INCLUDEDIR})
+
+# search the glibconfig.h include dir under the same root where the library is found
+find_library(GLIB2_LIBRARIES
+             NAMES glib-2.0
+             HINTS ${PKG_GLIB_LIBRARY_DIRS} ${PKG_GLIB_LIBDIR})
+
+find_path(GLIB2_INTERNAL_INCLUDE_DIR glibconfig.h
+          PATH_SUFFIXES glib-2.0/include ../lib/glib-2.0/include
+          HINTS ${PKG_GLIB_INCLUDE_DIRS} ${PKG_GLIB_LIBRARIES} ${CMAKE_SYSTEM_LIBRARY_PATH})
+
+set(GLIB2_INCLUDE_DIR ${GLIB2_MAIN_INCLUDE_DIR})
+
+# not sure if this include dir is optional or required
+# for now it is optional
+if(GLIB2_INTERNAL_INCLUDE_DIR)
+  set(GLIB2_INCLUDE_DIR ${GLIB2_INCLUDE_DIR} ${GLIB2_INTERNAL_INCLUDE_DIR})
+endif(GLIB2_INTERNAL_INCLUDE_DIR)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(GLIB2  DEFAULT_MSG  GLIB2_LIBRARIES GLIB2_MAIN_INCLUDE_DIR)
+
+mark_as_advanced(GLIB2_INCLUDE_DIR GLIB2_LIBRARIES)
+
+
+find_program(GLIB2_GENMARSHAL_UTIL glib-genmarshal)
+
+macro(glib2_genmarshal output_name)
+    file(REMOVE ${CMAKE_CURRENT_BINARY_DIR}/genmarshal_tmp)
+    foreach(_declaration ${ARGN})
+        file(APPEND ${CMAKE_CURRENT_BINARY_DIR}/genmarshal_tmp "${_declaration}\n")
+    endforeach()
+    add_custom_command(
+        OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${output_name}.h ${CMAKE_CURRENT_BINARY_DIR}/${output_name}.c
+        COMMAND ${GLIB2_GENMARSHAL_UTIL} --header genmarshal_tmp > ${output_name}.h
+        COMMAND ${GLIB2_GENMARSHAL_UTIL} --body genmarshal_tmp > ${output_name}.c
+        WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+    )
+endmacro()