Bug 40077: Don't pass --no-insert-timestamp when building Firefox

https://bugzilla.mozilla.org/show_bug.cgi?id=1612423 does that for us
now when using mingw-w64.

projects/firefox/build

@@ -77,8 +77,6 @@ fi
   # Make sure widl is not inserting random timestamps, see #21837.
   export WIDL_TIME_OVERRIDE="0"
   patch -p1 < $rootdir/nsis-uninstall.patch
-  # Make sure we link without inserting timestamps in general.
-  export LDFLAGS="-Wl,--no-insert-timestamp"
 [% END -%]
 
 [% IF c("var/namecoin") %]