Use LTDL_LIBRARY_PATH instead of (DY)LD_LIBRARY_PATH

With GnuCash's main libraries now linked at startup instead of being
dlopened at runtime except by Guile we can restrict the library path
renaming to Gnu Libtool's environment variable.

gnucash/environment.in

@@ -64,10 +64,7 @@ GUILE_LOAD_PATH=@GNC_GUILE_LOAD_PATH@;{GUILE_LIBS};{GUILE_LOAD_PATH}
 GUILE_LOAD_COMPILED_PATH=@GNC_GUILE_LOAD_COMPILED_PATH@;{GUILE_COMPILED_LIBS};{GUILE_LOAD_COMPILED_PATH}
 
 # Tell Guile where to find GnuCash specific shared libraries
-GNC_LIBRARY_PATH={SYS_LIB};{GNC_LIB}
-LD_LIBRARY_PATH={GNC_LIBRARY_PATH};{LD_LIBRARY_PATH}
-# The same, but for GnuCash on OS X
-DYLD_LIBRARY_PATH={GNC_LIBRARY_PATH};{DYLD_LIBRARY_PATH}
+LTDL_LIBRARY_PATH={SYS_LIB};{GNC_LIB}
 
 # For changing the language GnuCash uses, first refer to
 # to https://wiki.gnucash.org/wiki/Locale_Settings.