gccrs: Fix scan-gimpl testcases on BE platforms.

gcc/testsuite/ChangeLog:

	* rust/compile/builtin_macro_eager1.rs: Switch to scan-assembler
	directive as the GIMPLE dump does not contain strings on BE.
	* rust/compile/builtin_macro_recurse2.rs: Likewise.

gcc/testsuite/rust/compile/builtin_macro_eager1.rs

@@ -15,7 +15,7 @@ macro_rules! b {
 }
 
 fn main() {
-    // { dg-final { scan-tree-dump-times {"test1canary"} 1 gimple } }
+    // { dg-final { scan-assembler {"test1canary"} } }
     let _ = concat!(a!(), 1, b!());
     // should not error
     concat!(a!(), true, b!(),);

gcc/testsuite/rust/compile/builtin_macro_recurse2.rs

@@ -16,6 +16,6 @@ macro_rules! a {
 }
 
 fn main() {
-    // { dg-final { scan-tree-dump-times {"abheyho"} 1 gimple } }
+    // { dg-final { scan-assembler {"abheyho"} } }
     let _ = concat!("a", 'b', a!(), a!(b c d e f a!()), '\0');
 }