cmake: Remove unnessessary variables from configure_file() command (#39)

Just cleanup.

Output path is relative to build directory anyway according
to documentation.

Related to #9.

CMakeLists.txt

@@ -48,7 +48,7 @@ function(configure_pkg_config_file pkg_config_file_in)
     set(includedir ${CMAKE_INSTALL_FULL_INCLUDEDIR})
     set(VERSION ${PROJECT_VERSION})
     string(REPLACE ".in" "" pkg_config_file ${pkg_config_file_in})
-    configure_file(${pkg_config_file_in} ${CMAKE_CURRENT_BINARY_DIR}/${pkg_config_file} @ONLY)
+    configure_file(${pkg_config_file_in} ${pkg_config_file} @ONLY)
 endfunction()
 
 message(STATUS "Configuring ${PROJECT_NAME} ${PROJECT_VERSION}")
@@ -62,7 +62,7 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 
 include(CheckSizes)
 
-configure_file(include/ogg/config_types.h.in ${CMAKE_CURRENT_BINARY_DIR}/include/ogg/config_types.h @ONLY)
+configure_file(include/ogg/config_types.h.in include/ogg/config_types.h @ONLY)
 
 set(OGG_HEADERS
     ${CMAKE_CURRENT_BINARY_DIR}/include/ogg/config_types.h