oops forgot to update so file path in tests

Author: Ellen Arteca

tests/fail/extern-so/function_not_in_SO.rs

@@ -1,6 +1,6 @@
 //@only-target-linux
 //@only-on-host
-//@compile-flags: -Zmiri-extern-so-file=tests/extern-so/libtestlib.so
+//@compile-flags: -Zmiri-extern-so-file=target/miri-extern-so/libtestlib.so
 
 extern "C" {
     fn foo();

tests/pass/extern-so/call_extern_c_fcts.rs

@@ -1,6 +1,6 @@
 //@only-target-linux
 //@only-on-host
-//@compile-flags: -Zmiri-extern-so-file=tests/extern-so/libtestlib.so
+//@compile-flags: -Zmiri-extern-so-file=target/miri-extern-so/libtestlib.so
 
 extern "C" {
     fn add_one_int(x: i32) -> i32;