gnu: rust: Accept more detailed gdb lines for simple enums.

* gnu/packages/patches/rust-1.25-accept-more-detailed-gdb-lines.patch: Modify.
* gnu/packages/rust.scm (rust-1.25)[arguments]<#:phases>[disable-nil-enum-test]:
Delete phase.

gnu/packages/patches/rust-1.25-accept-more-detailed-gdb-lines.patch

@@ -92,3 +92,19 @@ diff -ur orig/rustc-1.25.0-src/src/test/debuginfo/generic-tuple-style-enum.rs ru
  
  // gdb-command:print univariant
  // gdbg-check:$4 = {{__0 = -1}}
+--- orig/rustc-1.25.0-src/src/test/debuginfo/nil-enum.rs	2018-09-13 10:24:33.783565071 +0200
++++ rustc-1.25.0-src/src/test/debuginfo/nil-enum.rs	2018-10-26 18:19:20.404564587 +0200
+@@ -17,11 +17,11 @@
+ 
+ // gdb-command:print first
+ // gdbg-check:$1 = {<No data fields>}
+-// gdbr-check:$1 = <error reading variable>
++// gdbr-check:$1 = nil_enum::ANilEnum
+ 
+ // gdb-command:print second
+ // gdbg-check:$2 = {<No data fields>}
+-// gdbr-check:$2 = <error reading variable>
++// gdbr-check:$2 = nil_enum::AnotherNilEnum
+ 
+ #![allow(unused_variables)]
+ #![feature(omit_gdb_pretty_printer_section)]

gnu/packages/rust.scm

@@ -706,13 +706,6 @@ (define-public rust-1.25
                    ;; This test wants to update the crate index.
                    (("fn no_index_update") "#[ignore]\nfn no_index_update"))
                  #t))
-             ;; FIXME: Re-enable this test if it's indeed supposed to work.
-             ;; See <https://github.com/rust-lang/rust/issues/54178>.
-             (add-after 'configure 'disable-nil-enum-test
-               (lambda _
-                 (substitute* "src/test/debuginfo/nil-enum.rs"
-                   (("ignore-lldb") "ignore-gdb"))
-                 #t))
              (replace 'patch-aarch64-test
                (lambda _
                  (substitute* "src/librustc_metadata/dynamic_lib.rs"