gnu: m4-boot0: Downgrade to 1.4.18.

* gnu/packages/commencement.scm (m4-boot0): Downgrade to 1.4.18.
[arguments]: Don't inherit from m4.  Add a phase to patch shell
invocations in the tests.  Add a phase when building for riscv64-linux
to skip a few tests.

Change-Id: Ide87b1dceec6a6a95a750e4cd561d7be166ffee2

gnu/packages/commencement.scm

@@ -3346,12 +3346,35 @@ (define m4-boot0
   (package
     (inherit m4)
     (name "m4-boot0")
-    (source (bootstrap-origin (package-source m4)))
+    (version "1.4.18")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append "mirror://gnu/m4/m4-" version ".tar.gz"))
+              (sha256
+               (base32 "1arz972zxmwhnyik9007g6ww9gars8d55xbvg548xlsw3a9369mb"))))
     (inputs (%boot0-inputs))
     (arguments
      `(#:guile ,%bootstrap-guile
        #:implicit-inputs? #f
-       ,@(package-arguments m4)
+       #:phases
+       (modify-phases %standard-phases
+         (add-before 'check 'pre-check
+           (lambda* (#:key inputs #:allow-other-keys)
+             (for-each patch-shebang (find-files "tests" "\\.sh$"))
+             (substitute* (find-files "tests" "posix_spawn")
+               (("/bin/sh")
+                (search-input-file inputs "/bin/sh")))))
+         ;; Better to skip some tests instead of all the tests.
+         ,@(if (target-riscv64?)
+               `((add-after 'unpack 'skip-some-tests
+                   (lambda _
+                     (substitute* "tests/Makefile.in"
+                       (("test-canonicalize-lgpl\\$\\(EXEEXT\\) ") "")
+                       (("test-localename\\$\\(EXEEXT\\) ") "")
+                       (("test-mbrtowc5.sh ") "")
+                       (("test-sigprocmask\\$\\(EXEEXT\\) ") "")
+                       ))))
+               `()))
        ;; Ignore test failure in gnulib for armhf/aarch64 and Hurd
        #:tests? ,(and (not (target-arm?))
                       (not (target-hurd?)))))))