gnu: doxygen: Work around GCC ICE on armhf-linux.

Reported by Mark H Weaver <mhw@netris.org>
at <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=31708#10>.

* gnu/packages/patches/doxygen-gcc-ice.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/documentation.scm (doxygen)[inputs]: Add "gcc-ice-patch"
on armhf-* only.
[arguments]: Add 'apply-gcc-patch' phase on armhf-* only.

gnu/local.mk

@@ -634,6 +634,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/docbook-xsl-nonrecursive-string-subst.patch	\
   %D%/packages/patches/doc++-include-directives.patch		\
   %D%/packages/patches/doc++-segfault-fix.patch			\
+  %D%/packages/patches/doxygen-gcc-ice.patch			\
   %D%/packages/patches/doxygen-test.patch			\
   %D%/packages/patches/dvd+rw-tools-add-include.patch 		\
   %D%/packages/patches/e2fsprogs-glibc-2.27.patch		\

gnu/packages/documentation.scm

@@ -139,10 +139,23 @@ markup) can be customized and extended by the user.")
        ("libxml2" ,libxml2) ; provides xmllint for the tests
        ("python" ,python-2))) ; for creating the documentation
     (inputs
-     `(("bash" ,bash-minimal)))
+     `(("bash" ,bash-minimal)
+       ,@(if (string-prefix? "armhf-" (%current-system))
+             `(("gcc-ice-patch" ,@(search-patches "doxygen-gcc-ice.patch")))
+             '())))
     (arguments
      `(#:test-target "tests"
        #:phases (modify-phases %standard-phases
+                  ;; Work around an ICE that shows up on native compiles for
+                  ;; armhf-linux.
+                  ,@(if (string-prefix? "armhf-" (%current-system))
+                        `((add-after 'unpack 'apply-gcc-patch
+                            (lambda* (#:key inputs #:allow-other-keys)
+                              (let ((patch (assoc-ref inputs "gcc-ice-patch")))
+                                (invoke "patch" "-p1" "--force"
+                                        "--input" patch)))))
+                        '())
+
                   (add-before 'configure 'patch-sh
                               (lambda* (#:key inputs #:allow-other-keys)
                                 (substitute* "src/portable.cpp"

gnu/packages/patches/doxygen-gcc-ice.patch

@@ -0,0 +1,25 @@
+Work around this GCC ICE: <https://bugs.gnu.org/31708>.  It shows up
+only when doing native compiles on armhf-linux.
+
+Yes it's a terrible patch, but it does the job.
+
+--- doxygen-1.8.13/qtools/qutfcodec.cpp	1970-01-01 01:00:00.000000000 +0100
++++ doxygen-1.8.13/qtools/qutfcodec.cpp	2018-06-08 14:14:29.614009929 +0200
+@@ -189,7 +189,7 @@ int QUtf16Codec::heuristicContentMatch(c
+ }
+ 
+ 
+-
++volatile const void *bomPointer = &QChar::byteOrderMark;
+ 
+ class QUtf16Encoder : public QTextEncoder {
+     bool headerdone;
+@@ -209,7 +209,7 @@ public:
+ 	    headerdone = TRUE;
+ 	    len_in_out = (1+uc.length())*(int)sizeof(QChar);
+ 	    QCString d(len_in_out);
+-	    memcpy(d.rawData(),&QChar::byteOrderMark,sizeof(QChar));
++	    memcpy(d.rawData(),(void *)bomPointer,sizeof(QChar));
+ 	    memcpy(d.rawData()+sizeof(QChar),uc.unicode(),uc.length()*sizeof(QChar));
+ 	    return d;
+ 	}