tests: basic-[debugger-]stepping.rs: Disable SingleUseConsts MIR pass

To make more of the test pass. It should not be necessary to disable
this pass, but by doing it we can avoid further regressions while we
figure out how to solve this use case properly.

The last two `FIXME(33013)` didn't go away from this change, only the
first six. But that can be investigated separately.

Author: Enselic

tests/debuginfo/basic-stepping.rs

@@ -5,7 +5,8 @@
 //@ ignore-aarch64: Doesn't work yet.
 //@ ignore-loongarch64: Doesn't work yet.
 //@ ignore-riscv64: Doesn't work yet.
-//@ compile-flags: -g
+// FIXME: It should not be necessary to disable SingleUseConsts
+//@ compile-flags: -g -Zmir-enable-passes=-SingleUseConsts
 
 // gdb-command: run
 // FIXME(#97083): Should we be able to break on initialization of zero-sized types?
@@ -14,12 +15,12 @@
 // gdb-command: next
 // gdb-check:   let d = c = 99;
 // gdb-command: next
-// FIXME(#33013): gdb-check:   let e = "hi bob";
-// FIXME(#33013): gdb-command: next
-// FIXME(#33013): gdb-check:   let f = b"hi bob";
-// FIXME(#33013): gdb-command: next
-// FIXME(#33013): gdb-check:   let g = b'9';
-// FIXME(#33013): gdb-command: next
+// gdb-check:   let e = "hi bob";
+// gdb-command: next
+// gdb-check:   let f = b"hi bob";
+// gdb-command: next
+// gdb-check:   let g = b'9';
+// gdb-command: next
 // FIXME(#33013): gdb-check:   let h = ["whatever"; 8];
 // FIXME(#33013): gdb-command: next
 // gdb-check:   let i = [1,2,3,4];