gnu: libsigrokdecode: Fix build with python 3.9.

* gnu/packages/patches/libsigrokdecode-python3.9-fix.patch: New file.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/electronics.scm (libsigrokdecode)[native-inputs]: Add
automake, autoconf.
[source](patches): New field.

gnu/local.mk

@@ -1474,6 +1474,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/mcrypt-CVE-2012-4527.patch			\
   %D%/packages/patches/libmemcached-build-with-gcc7.patch	\
   %D%/packages/patches/libmhash-hmac-fix-uaf.patch		\
+  %D%/packages/patches/libsigrokdecode-python3.9-fix.patch	\
   %D%/packages/patches/mercurial-hg-extension-path.patch       \
   %D%/packages/patches/mesa-opencl-all-targets.patch		\
   %D%/packages/patches/mesa-skip-tests.patch			\

gnu/packages/electronics.scm

@@ -29,6 +29,7 @@
   #:use-module (guix build-system cmake)
   #:use-module (gnu packages)
   #:use-module (gnu packages algebra)
+  #:use-module (gnu packages autotools)
   #:use-module (gnu packages base)
   #:use-module (gnu packages bash)
   #:use-module (gnu packages boost)
@@ -78,11 +79,18 @@ to take care of the OS-specific details when writing software that uses serial p
                     version ".tar.gz"))
               (sha256
                (base32
-                "1h1zi1kpsgf6j2z8j8hjpv1q7n49i3fhqjn8i178rka3cym18265"))))
+                "1h1zi1kpsgf6j2z8j8hjpv1q7n49i3fhqjn8i178rka3cym18265"))
+              (patches
+               (search-patches "libsigrokdecode-python3.9-fix.patch"))))
     (outputs '("out" "doc"))
     (arguments
      `(#:phases
        (modify-phases %standard-phases
+         (replace 'bootstrap
+           (lambda _
+             (invoke "autoconf")
+             (invoke "aclocal")
+             (invoke "automake" "-ac")))
          (add-after 'build 'build-doc
            (lambda _
              (invoke "doxygen")
@@ -94,7 +102,7 @@ to take care of the OS-specific details when writing software that uses serial p
                                               "/share/doc/libsigrokdecode"))
              #t)))))
     (native-inputs
-     (list check-0.14 doxygen graphviz pkg-config))
+     (list check-0.14 doxygen graphviz pkg-config automake autoconf))
     ;; libsigrokdecode.pc lists "python" in Requires.private, and "glib" in Requires.
     (propagated-inputs
      (list glib python))

gnu/packages/patches/libsigrokdecode-python3.9-fix.patch

@@ -0,0 +1,19 @@
+From: Dan Horák <dan@danny.cz>
+Subject: Add support for Python 3.9
+
+Origin: upstream, https://sigrok.org/gitweb/?p=libsigrokdecode.git;a=commitdiff;h=9b0ad5177bd692f7556a4756bdbd2da81d9c34ce
+Bug-Debian: https://bugs.debian.org/972769
+
+diff --git a/configure.ac b/configure.ac
+index f9958b3..2917cb3 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -100,7 +100,7 @@ SR_PKG_CHECK_SUMMARY([srd_pkglibs_summary])
+ # first, since usually only that variant will add "-lpython3.8".
+ # https://docs.python.org/3/whatsnew/3.8.html#debug-build-uses-the-same-abi-as-release-build
+ SR_PKG_CHECK([python3], [SRD_PKGLIBS],
+-	[python-3.8-embed], [python-3.8 >= 3.8], [python-3.7 >= 3.7], [python-3.6 >= 3.6], [python-3.5 >= 3.5], [python-3.4 >= 3.4], [python-3.3 >= 3.3], [python-3.2 >= 3.2], [python3 >= 3.2])
++	[python-3.9-embed], [python-3.8-embed], [python-3.8 >= 3.8], [python-3.7 >= 3.7], [python-3.6 >= 3.6], [python-3.5 >= 3.5], [python-3.4 >= 3.4], [python-3.3 >= 3.3], [python-3.2 >= 3.2], [python3 >= 3.2])
+ AS_IF([test "x$sr_have_python3" = xno],
+ 	[AC_MSG_ERROR([Cannot find Python 3 development headers.])])
+