Remove static linking hack since we are now passing absolute paths

Author: nikomatsakis

src/test/run-pass/command-before-exec.rs

@@ -9,8 +9,6 @@
 // except according to those terms.
 
 // ignore-windows - this is a unix-specific test
-// no-prefer-dynamic - this test breaks with dynamic linking as
-// some LD_LIBRARY_PATH entries are relative and it cd's to /.
 
 #![feature(process_exec, libc)]