respect the libdir cmake already set up for us instead of using debian-specific multiarch paths

--- apitrace-7.1/CMakeLists.txt
+++ apitrace-7.1/CMakeLists.txt
@@ -359,15 +359,6 @@
 ##############################################################################
 # Installation directories
 
-if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
-    # Debian multiarch support
-    execute_process(COMMAND dpkg-architecture -qDEB_HOST_MULTIARCH
-        OUTPUT_VARIABLE ARCH_SUBDIR
-        ERROR_QUIET
-        OUTPUT_STRIP_TRAILING_WHITESPACE
-    )
-endif()
-
 if (WIN32 OR APPLE)
     # On Windows/MacOSX, applications are usually installed on a directory of
     # their own
@@ -376,12 +367,8 @@
     set (LIB_ARCH_INSTALL_DIR lib)
 else ()
     set (DOC_INSTALL_DIR share/doc/${CMAKE_PROJECT_NAME})
-    set (LIB_INSTALL_DIR lib${LIB_SUFFIX}/${CMAKE_PROJECT_NAME})
-    if (ARCH_SUBDIR)
-        set (LIB_ARCH_INSTALL_DIR lib/${ARCH_SUBDIR}/${CMAKE_PROJECT_NAME})
-    else ()
-        set (LIB_ARCH_INSTALL_DIR lib${LIB_SUFFIX}/${CMAKE_PROJECT_NAME})
-    endif ()
+    set (LIB_INSTALL_DIR ${CMAKE_INSTALL_LIBDIR}/${CMAKE_PROJECT_NAME})
+    set (LIB_ARCH_INSTALL_DIR ${LIB_INSTALL_DIR})
 endif ()
 
 set (SCRIPTS_INSTALL_DIR ${LIB_INSTALL_DIR}/scripts)