Make the pkgconfig.in libdir variable reference the real installed library directory.
diff --git a/src/pkgconfig.in b/src/pkgconfig.in
index 1e2e6cd..d4c3752 100644
--- a/src/pkgconfig.in
+++ b/src/pkgconfig.in
@@ -1,7 +1,7 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
 includedir=${prefix}/include
-libdir=${prefix}/lib
+libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
 
 Name: @CMAKE_PROJECT_NAME@
 Description: @NN_DESCRIPTION@